PHP Tutorial
PHP is a server scripting language, and a powerful tool for making dynamic and interactive Web pages.
PHP is a widely-used, free, and efficient alternative to competitors such as Microsoft's ASP.
PHP 7 is the latest stable release.
Easy Learning with "PHP Tryit"
With our online "PHP Tryit" editor, you can edit the PHP code, and click on a button to view the result.
Example
PHP Introduction
PHP code is executed on the server.
What You Should Already Know
Before you continue you should have a basic understanding of the following:
HTML
CSS
JavaScript
If you want to study these subjects first, find the tutorials on our Home page.
What is PHP?
PHP is an acronym for "PHP: Hypertext Preprocessor"
PHP is a widely-used, open source scripting language
PHP scripts are executed on the server
PHP is free to download and use
PHP is an amazing and popular language!
It is powerful enough to be at the core of the biggest blogging system on the web (WordPress)!
It is deep enough to run the largest social network (Facebook)!
It is also easy enough to be a beginner's first server side language!
What is a PHP File?
PHP files can contain text, HTML, CSS, JavaScript, and PHP code
PHP code is executed on the server, and the result is returned to the browser as plain HTML
PHP files have extension ".php"
What Can PHP Do?
PHP can generate dynamic page content
PHP can create, open, read, write, delete, and close files on the server
PHP can collect form data
PHP can send and receive cookies
PHP can add, delete, modify data in your database
PHP can be used to control user-access
PHP can encrypt data
With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.
Why PHP?
PHP runs on various platforms (Windows, Linux, Unix, Mac OS X, etc.)
PHP is compatible with almost all servers used today (Apache, IIS, etc.)
PHP supports a wide range of databases
PHP is free. Download it from the official PHP resource: www.php.net
PHP is easy to learn and runs efficiently on the server side
What's new in PHP 7
PHP 7 is much faster than the previous popular stable release (PHP 5.6)
PHP 7 has improved Error Handling
PHP 7 supports stricter Type Declarations for function arguments
PHP 7 supports new operators (like the spaceship operator: <=>)
PHP Installation
What Do I Need?
To start using PHP, you can:
Find a web host with PHP and MySQL support
Install a web server on your own PC, and then install PHP and MySQL
Use a Web Host With PHP Support
If your server has activated support for PHP you do not need to do anything.
Just create some .php files, place them in your web directory, and the server will automatically parse them for you.
You do not need to compile anything or install any extra tools.
Because PHP is free, most web hosts offer PHP support.
Set Up PHP on Your Own PC
However, if your server does not support PHP, you must:
install a web server
install PHP
install a database, such as MySQL
The official PHP website (PHP.net) has installation instructions for PHP: http://php.net/manual/en/install.php
PHP Online Compiler / Editor
With w3schools' online PHP compiler, you can edit PHP code, and view the result in your browser.
I love PHP!
PHP Syntax
A PHP script is executed on the server, and the plain HTML result is sent back to the browser.
Basic PHP Syntax
A PHP script can be placed anywhere in the document.
A PHP script starts with :
The default file extension for PHP files is ".php".
A PHP file normally contains HTML tags, and some PHP scripting code.
Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function "echo" to output the text "Hello World!" on a web page:
Example
"; EcHo "Hello World!
"; ?> Note: However; all variable names are case-sensitive! Look at the example below; only the first statement will display the value of the $color variable! This is because $color, $COLOR, and $coLOR are treated as three different variables: Example "; echo "My house is " . $COLOR . "
"; echo "My boat is " . $coLOR . "
"; ?> PHP Comments Comments in PHP A comment in PHP code is a line that is not executed as a part of the program. Its only purpose is to be read by someone who is looking at the code. Comments can be used to: Let others understand your code Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code PHP supports several ways of commenting: Example Syntax for single-line comments: Example Syntax for multiple-line comments: Example Using comments to leave out parts of the code: PHP Variables Variables are "containers" for storing information. Creating (Declaring) PHP Variables In PHP, a variable starts with the $ sign, followed by the name of the variable: Example After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5. Note: When you assign a text value to a variable, put quotes around the value. Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it. Think of variables as containers for storing data. PHP Variables A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for PHP variables: A variable starts with the $ sign, followed by the name of the variable A variable name must start with a letter or the underscore character A variable name cannot start with a number A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) Variable names are case-sensitive ($age and $AGE are two different variables) Remember that PHP variable names are case-sensitive! Output Variables The PHP echo statement is often used to output data to the screen. The following example will show how to output text and a variable: Example The following example will produce the same output as the example above: Example The following example will output the sum of two variables: Example Note: You will learn more about the echo statement and how to output data to the screen in the next chapter. PHP is a Loosely Typed Language In the example above, notice that we did not have to tell PHP which data type the variable is. PHP automatically associates a data type to the variable, depending on its value. Since the data types are not set in a strict sense, you can do things like adding a string to an integer without causing an error. In PHP 7, type declarations were added. This gives an option to specify the data type expected when declaring a function, and by enabling the strict requirement, it will throw a "Fatal Error" on a type mismatch. PHP Variables Scope PHP Variables Scope In PHP, variables can be declared anywhere in the script. The scope of a variable is the part of the script where the variable can be referenced/used. PHP has three different variable scopes: local global static Global and Local Scope A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function: Example Variable with global scope: Variable x inside function is: $x"; } myTest(); echo "
"; echo "I'm about to learn PHP!
"; echo "This ", "string ", "was ", "made ", "with multiple parameters."; ?> Display Variables The following example shows how to output text and variables with the echo statement: Example " . $txt1 . ""; echo "Study PHP at " . $txt2 . "
"; echo $x + $y; ?> The PHP print Statement The print statement can be used with or without parentheses: print or print(). Display Text The following example shows how to output text with the print command (notice that the text can contain HTML markup): Example PHP is Fun!"; print "Hello world!
"; print "I'm about to learn PHP!"; ?> Display Variables The following example shows how to output text and variables with the print statement: Example " . $txt1 . ""; print "Study PHP at " . $txt2 . "
"; print $x + $y; ?> PHP Data Types PHP Data Types Variables can store data of different types, and different data types can do different things. PHP supports the following data types: String Integer Float (floating point numbers - also called double) Boolean Array Object NULL Resource PHP String A string is a sequence of characters, like "Hello world!". A string can be any text inside quotes. You can use single or double quotes: Example "; echo $y; ?> PHP Integer An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647. Rules for integers: An integer must have at least one digit An integer must not have a decimal point An integer can be either positive or negative Integers can be specified in: decimal (base 10), hexadecimal (base 16), octal (base 8), or binary (base 2) notation In the following example $x is an integer. The PHP var_dump() function returns the data type and value: Example PHP Float A float (floating point number) is a number with a decimal point or a number in exponential form. In the following example $x is a float. The PHP var_dump() function returns the data type and value: Example PHP Boolean A Boolean represents two possible states: TRUE or FALSE. $x = true; $y = false; Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial. PHP Array An array stores multiple values in one single variable. In the following example $cars is an array. The PHP var_dump() function returns the data type and value: Example You will learn a lot more about arrays in later chapters of this tutorial. PHP Object Classes and objects are the two main aspects of object-oriented programming. A class is a template for objects, and an object is an instance of a class. When the individual objects are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties. Let's assume we have a class named Car. A Car can have properties like model, color, etc. We can define variables like $model, $color, and so on, to hold the values of these properties. When the individual objects (Volvo, BMW, Toyota, etc.) are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties. If you create a __construct() function, PHP will automatically call this function when you create an object from a class. Example color = $color; $this->model = $model; } public function message() { return "My car is a " . $this->color . " " . $this->model . "!"; } } $myCar = new Car("black", "Volvo"); echo $myCar -> message(); echo "
"; $myCar = new Car("red", "Toyota"); echo $myCar -> message(); ?> PHP NULL Value Null is a special data type which can have only one value: NULL. A variable of data type NULL is a variable that has no value assigned to it. Tip: If a variable is created without a value, it is automatically assigned a value of NULL. Variables can also be emptied by setting the value to NULL: Example PHP Resource The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP. A common example of using the resource data type is a database call. PHP Strings A string is a sequence of characters, like "Hello world!". PHP String Functions In this chapter we will look at some commonly used functions to manipulate strings. strlen() - Return the Length of a String The PHP strlen() function returns the length of a string. Example Return the length of the string "Hello world!": str_word_count() - Count Words in a String The PHP str_word_count() function counts the number of words in a string. Example Count the number of word in the string "Hello world!": strrev() - Reverse a String The PHP strrev() function reverses a string. Example Reverse the string "Hello world!": strpos() - Search For a Text Within a String The PHP strpos() function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE. Example Search for the text "world" in the string "Hello world!": Tip: The first character position in a string is 0 (not 1). str_replace() - Replace Text Within a String The PHP str_replace() function replaces some characters with some other characters in a string. Example Replace the text "world" with "Dolly": Complete PHP String Reference For a complete reference of all string functions, go to our complete PHP String Reference. The PHP string reference contains description and example of use, for each function! PHP Numbers In this chapter we will look in depth into Integers, Floats, and Number Strings. PHP Numbers One thing to notice about PHP is that it provides automatic data type conversion. So, if you assign an integer value to a variable, the type of that variable will automatically be an integer. Then, if you assign a string to the same variable, the type will change to a string. This automatic conversion can sometimes break your code. PHP Integers An integer is a number without any decimal part. 2, 256, -256, 10358, -179567 are all integers. While 7.56, 10.0, 150.67 are floats. So, an integer data type is a non-decimal number between -2147483648 and 2147483647. A value greater (or lower) than this, will be stored as float, because it exceeds the limit of an integer. Another important thing to know is that even if 4 * 2.5 is 10, the result is stored as float, because one of the operands is a float (2.5). Here are some rules for integers: An integer must have at least one digit An integer must not have a decimal point An integer can be either positive or negative Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0) PHP has the following functions to check if the type of a variable is integer: is_int() is_integer() - alias of is_int() is_long() - alias of is_int() Example Check if the type of a variable is integer: PHP Floats A float is a number with a decimal point or a number in exponential form. 2.0, 256.4, 10.358, 7.64E+5, 5.56E-5 are all floats. The float data type can commonly store a value up to 1.7976931348623E+308 (platform dependent), and have a maximum precision of 14 digits. PHP has the following functions to check if the type of a variable is float: is_float() is_double() - alias of is_float() Example Check if the type of a variable is float: PHP Infinity A numeric value that is larger than PHP_FLOAT_MAX is considered infinite. PHP has the following functions to check if a numeric value is finite or infinite: is_finite() is_infinite() However, the PHP var_dump() function returns the data type and value: Example Check if a numeric value is finite or infinite: PHP NaN NaN stands for Not a Number. NaN is used for impossible mathematical operations. PHP has the following functions to check if a value is not a number: is_nan() However, the PHP var_dump() function returns the data type and value: Example Invalid calculation will return a NaN value: PHP Numerical Strings The PHP is_numeric() function can be used to find whether a variable is numeric. The function returns true if the variable is a number or a numeric string, false otherwise. Example Check if the variable is numeric: Note: From PHP 7.0: The is_numeric() function will return FALSE for numeric strings in hexadecimal form (e.g. 0xf4c3b00c), as they are no longer considered as numeric strings. PHP Casting Strings and Floats to Integers Sometimes you need to cast a numerical value into another data type. The (int), (integer), or intval() function are often used to convert a value to an integer. Example Cast float and string to integer: "; // Cast string to int $x = "23465.768"; $int_cast = (int)$x; echo $int_cast; ?> PHP Math PHP has a set of math functions that allows you to perform mathematical tasks on numbers. PHP pi() Function The pi() function returns the value of PI: Example PHP min() and max() Functions The min() and max() functions can be used to find the lowest or highest value in a list of arguments: Example PHP abs() Function The abs() function returns the absolute (positive) value of a number: Example PHP sqrt() Function The sqrt() function returns the square root of a number: Example PHP round() Function The round() function rounds a floating-point number to its nearest integer: Example Random Numbers The rand() function generates a random number: Example To get more control over the random number, you can add the optional min and max parameters to specify the lowest integer and the highest integer to be returned. For example, if you want a random integer between 10 and 100 (inclusive), use rand(10, 100): Example PHP Constants Constants are like variables except that once they are defined they cannot be changed or undefined. PHP Constants A constant is an identifier (name) for a simple value. The value cannot be changed during the script. A valid constant name starts with a letter or underscore (no $ sign before the constant name). Note: Unlike variables, constants are automatically global across the entire script. Create a PHP Constant To create a constant, use the define() function. Syntax define(name, value, case-insensitive) Parameters: name: Specifies the name of the constant value: Specifies the value of the constant case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false Example Create a constant with a case-sensitive name: Example Create a constant with a case-insensitive name: PHP Constant Arrays In PHP7, you can create an Array constant using the define() function. Example Create an Array constant: Constants are Global Constants are automatically global and can be used across the entire script. Example This example uses a constant inside a function, even if it is defined outside the function: PHP Operators PHP Operators Operators are used to perform operations on variables and values. PHP divides the operators in the following groups: Arithmetic operators Assignment operators Comparison operators Increment/Decrement operators Logical operators String operators Array operators Conditional assignment operators PHP Arithmetic Operators The PHP arithmetic operators are used with numeric values to perform common arithmetical operations, such as addition, subtraction, multiplication etc. Operator Name Example Result Show it + Addition $x + $y Sum of $x and $y - Subtraction $x - $y Difference of $x and $y * Multiplication $x * $y Product of $x and $y / Division $x / $y Quotient of $x and $y % Modulus $x % $y Remainder of $x divided by $y ** Exponentiation $x ** $y Result of raising $x to the $y'th power PHP Assignment Operators The PHP assignment operators are used with numeric values to write a value to a variable. The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right. Assignment Same as... Description Show it x = y x = y The left operand gets set to the value of the expression on the right x += y x = x + y Addition x -= y x = x - y Subtraction x *= y x = x * y Multiplication x /= y x = x / y Division x %= y x = x % y Modulus PHP Comparison Operators The PHP comparison operators are used to compare two values (number or string): Operator Name Example Result Show it == Equal $x == $y Returns true if $x is equal to $y === Identical $x === $y Returns true if $x is equal to $y, and they are of the same type != Not equal $x != $y Returns true if $x is not equal to $y <> Not equal $x <> $y Returns true if $x is not equal to $y !== Not identical $x !== $y Returns true if $x is not equal to $y, or they are not of the same type > Greater than $x > $y Returns true if $x is greater than $y < Less than $x < $y Returns true if $x is less than $y >= Greater than or equal to $x >= $y Returns true if $x is greater than or equal to $y <= Less than or equal to $x <= $y Returns true if $x is less than or equal to $y <=> Spaceship $x <=> $y Returns an integer less than, equal to, or greater than zero, depending on if $x is less than, equal to, or greater than $y. Introduced in PHP 7. PHP Increment / Decrement Operators The PHP increment operators are used to increment a variable's value. The PHP decrement operators are used to decrement a variable's value. Operator Name Description Show it ++$x Pre-increment Increments $x by one, then returns $x $x++ Post-increment Returns $x, then increments $x by one --$x Pre-decrement Decrements $x by one, then returns $x $x-- Post-decrement Returns $x, then decrements $x by one PHP Logical Operators The PHP logical operators are used to combine conditional statements. Operator Name Example Result Show it and And $x and $y True if both $x and $y are true or Or $x or $y True if either $x or $y is true xor Xor $x xor $y True if either $x or $y is true, but not both && And $x && $y True if both $x and $y are true || Or $x || $y True if either $x or $y is true ! Not !$x True if $x is not true PHP String Operators PHP has two operators that are specially designed for strings. Operator Name Example Result Show it . Concatenation $txt1 . $txt2 Concatenation of $txt1 and $txt2 .= Concatenation assignment $txt1 .= $txt2 Appends $txt2 to $txt1 PHP Array Operators The PHP array operators are used to compare arrays. Operator Name Example Result Show it + Union $x + $y Union of $x and $y == Equality $x == $y Returns true if $x and $y have the same key/value pairs === Identity $x === $y Returns true if $x and $y have the same key/value pairs in the same order and of the same types != Inequality $x != $y Returns true if $x is not equal to $y <> Inequality $x <> $y Returns true if $x is not equal to $y !== Non-identity $x !== $y Returns true if $x is not identical to $y PHP Conditional Assignment Operators The PHP conditional assignment operators are used to set a value depending on conditions: Operator Name Example Result Show it ?: Ternary $x = expr1 ? expr2 : expr3 Returns the value of $x. The value of $x is expr2 if expr1 = TRUE. The value of $x is expr3 if expr1 = FALSE ?? Null coalescing $x = expr1 ?? expr2 Returns the value of $x. The value of $x is expr1 if expr1 exists, and is not NULL. If expr1 does not exist, or is NULL, the value of $x is expr2. Introduced in PHP 7
My first PHP page
Note: PHP statements end with a semicolon (;). PHP Case Sensitivity In PHP, keywords (e.g. if, else, while, echo, etc.), classes, functions, and user-defined functions are not case-sensitive. In the example below, all three echo statements below are equal and legal: Example "; echo "Hello World!"; EcHo "Hello World!
"; ?> Note: However; all variable names are case-sensitive! Look at the example below; only the first statement will display the value of the $color variable! This is because $color, $COLOR, and $coLOR are treated as three different variables: Example "; echo "My house is " . $COLOR . "
"; echo "My boat is " . $coLOR . "
"; ?> PHP Comments Comments in PHP A comment in PHP code is a line that is not executed as a part of the program. Its only purpose is to be read by someone who is looking at the code. Comments can be used to: Let others understand your code Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re-figure out what they did. Comments can remind you of what you were thinking when you wrote the code PHP supports several ways of commenting: Example Syntax for single-line comments: Example Syntax for multiple-line comments: Example Using comments to leave out parts of the code: PHP Variables Variables are "containers" for storing information. Creating (Declaring) PHP Variables In PHP, a variable starts with the $ sign, followed by the name of the variable: Example After the execution of the statements above, the variable $txt will hold the value Hello world!, the variable $x will hold the value 5, and the variable $y will hold the value 10.5. Note: When you assign a text value to a variable, put quotes around the value. Note: Unlike other programming languages, PHP has no command for declaring a variable. It is created the moment you first assign a value to it. Think of variables as containers for storing data. PHP Variables A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for PHP variables: A variable starts with the $ sign, followed by the name of the variable A variable name must start with a letter or the underscore character A variable name cannot start with a number A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) Variable names are case-sensitive ($age and $AGE are two different variables) Remember that PHP variable names are case-sensitive! Output Variables The PHP echo statement is often used to output data to the screen. The following example will show how to output text and a variable: Example The following example will produce the same output as the example above: Example The following example will output the sum of two variables: Example Note: You will learn more about the echo statement and how to output data to the screen in the next chapter. PHP is a Loosely Typed Language In the example above, notice that we did not have to tell PHP which data type the variable is. PHP automatically associates a data type to the variable, depending on its value. Since the data types are not set in a strict sense, you can do things like adding a string to an integer without causing an error. In PHP 7, type declarations were added. This gives an option to specify the data type expected when declaring a function, and by enabling the strict requirement, it will throw a "Fatal Error" on a type mismatch. PHP Variables Scope PHP Variables Scope In PHP, variables can be declared anywhere in the script. The scope of a variable is the part of the script where the variable can be referenced/used. PHP has three different variable scopes: local global static Global and Local Scope A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function: Example Variable with global scope: Variable x inside function is: $x"; } myTest(); echo "
Variable x outside function is: $x
"; ?> A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function: Example Variable with local scope: Variable x inside function is: $x"; } myTest(); // using x outside the function will generate an error echo "Variable x outside function is: $x
"; ?> You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared. PHP The global Keyword The global keyword is used to access a global variable from within a function. To do this, use the global keyword before the variables (inside the function): Example PHP also stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable. This array is also accessible from within functions and can be used to update global variables directly. The example above can be rewritten like this: Example PHP The static Keyword Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job. To do this, use the static keyword when you first declare the variable: Example Then, each time the function is called, that variable will still have the information it contained from the last time the function was called. Note: The variable is still local to the function. PHP echo and print Statements With PHP, there are two basic ways to get output: echo and print. In this tutorial we use echo or print in almost every example. So, this chapter contains a little more info about those two output statements. PHP echo and print Statements echo and print are more or less the same. They are both used to output data to the screen. The differences are small: echo has no return value while print has a return value of 1 so it can be used in expressions. echo can take multiple parameters (although such usage is rare) while print can take one argument. echo is marginally faster than print. The PHP echo Statement The echo statement can be used with or without parentheses: echo or echo(). Display Text The following example shows how to output text with the echo command (notice that the text can contain HTML markup): Example PHP is Fun!"; echo "Hello world!"; echo "I'm about to learn PHP!
"; echo "This ", "string ", "was ", "made ", "with multiple parameters."; ?> Display Variables The following example shows how to output text and variables with the echo statement: Example " . $txt1 . ""; echo "Study PHP at " . $txt2 . "
"; echo $x + $y; ?> The PHP print Statement The print statement can be used with or without parentheses: print or print(). Display Text The following example shows how to output text with the print command (notice that the text can contain HTML markup): Example PHP is Fun!"; print "Hello world!
"; print "I'm about to learn PHP!"; ?> Display Variables The following example shows how to output text and variables with the print statement: Example " . $txt1 . ""; print "Study PHP at " . $txt2 . "
"; print $x + $y; ?> PHP Data Types PHP Data Types Variables can store data of different types, and different data types can do different things. PHP supports the following data types: String Integer Float (floating point numbers - also called double) Boolean Array Object NULL Resource PHP String A string is a sequence of characters, like "Hello world!". A string can be any text inside quotes. You can use single or double quotes: Example "; echo $y; ?> PHP Integer An integer data type is a non-decimal number between -2,147,483,648 and 2,147,483,647. Rules for integers: An integer must have at least one digit An integer must not have a decimal point An integer can be either positive or negative Integers can be specified in: decimal (base 10), hexadecimal (base 16), octal (base 8), or binary (base 2) notation In the following example $x is an integer. The PHP var_dump() function returns the data type and value: Example PHP Float A float (floating point number) is a number with a decimal point or a number in exponential form. In the following example $x is a float. The PHP var_dump() function returns the data type and value: Example PHP Boolean A Boolean represents two possible states: TRUE or FALSE. $x = true; $y = false; Booleans are often used in conditional testing. You will learn more about conditional testing in a later chapter of this tutorial. PHP Array An array stores multiple values in one single variable. In the following example $cars is an array. The PHP var_dump() function returns the data type and value: Example You will learn a lot more about arrays in later chapters of this tutorial. PHP Object Classes and objects are the two main aspects of object-oriented programming. A class is a template for objects, and an object is an instance of a class. When the individual objects are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties. Let's assume we have a class named Car. A Car can have properties like model, color, etc. We can define variables like $model, $color, and so on, to hold the values of these properties. When the individual objects (Volvo, BMW, Toyota, etc.) are created, they inherit all the properties and behaviors from the class, but each object will have different values for the properties. If you create a __construct() function, PHP will automatically call this function when you create an object from a class. Example color = $color; $this->model = $model; } public function message() { return "My car is a " . $this->color . " " . $this->model . "!"; } } $myCar = new Car("black", "Volvo"); echo $myCar -> message(); echo "
"; $myCar = new Car("red", "Toyota"); echo $myCar -> message(); ?> PHP NULL Value Null is a special data type which can have only one value: NULL. A variable of data type NULL is a variable that has no value assigned to it. Tip: If a variable is created without a value, it is automatically assigned a value of NULL. Variables can also be emptied by setting the value to NULL: Example PHP Resource The special resource type is not an actual data type. It is the storing of a reference to functions and resources external to PHP. A common example of using the resource data type is a database call. PHP Strings A string is a sequence of characters, like "Hello world!". PHP String Functions In this chapter we will look at some commonly used functions to manipulate strings. strlen() - Return the Length of a String The PHP strlen() function returns the length of a string. Example Return the length of the string "Hello world!": str_word_count() - Count Words in a String The PHP str_word_count() function counts the number of words in a string. Example Count the number of word in the string "Hello world!": strrev() - Reverse a String The PHP strrev() function reverses a string. Example Reverse the string "Hello world!": strpos() - Search For a Text Within a String The PHP strpos() function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE. Example Search for the text "world" in the string "Hello world!": Tip: The first character position in a string is 0 (not 1). str_replace() - Replace Text Within a String The PHP str_replace() function replaces some characters with some other characters in a string. Example Replace the text "world" with "Dolly": Complete PHP String Reference For a complete reference of all string functions, go to our complete PHP String Reference. The PHP string reference contains description and example of use, for each function! PHP Numbers In this chapter we will look in depth into Integers, Floats, and Number Strings. PHP Numbers One thing to notice about PHP is that it provides automatic data type conversion. So, if you assign an integer value to a variable, the type of that variable will automatically be an integer. Then, if you assign a string to the same variable, the type will change to a string. This automatic conversion can sometimes break your code. PHP Integers An integer is a number without any decimal part. 2, 256, -256, 10358, -179567 are all integers. While 7.56, 10.0, 150.67 are floats. So, an integer data type is a non-decimal number between -2147483648 and 2147483647. A value greater (or lower) than this, will be stored as float, because it exceeds the limit of an integer. Another important thing to know is that even if 4 * 2.5 is 10, the result is stored as float, because one of the operands is a float (2.5). Here are some rules for integers: An integer must have at least one digit An integer must not have a decimal point An integer can be either positive or negative Integers can be specified in three formats: decimal (10-based), hexadecimal (16-based - prefixed with 0x) or octal (8-based - prefixed with 0) PHP has the following functions to check if the type of a variable is integer: is_int() is_integer() - alias of is_int() is_long() - alias of is_int() Example Check if the type of a variable is integer: PHP Floats A float is a number with a decimal point or a number in exponential form. 2.0, 256.4, 10.358, 7.64E+5, 5.56E-5 are all floats. The float data type can commonly store a value up to 1.7976931348623E+308 (platform dependent), and have a maximum precision of 14 digits. PHP has the following functions to check if the type of a variable is float: is_float() is_double() - alias of is_float() Example Check if the type of a variable is float: PHP Infinity A numeric value that is larger than PHP_FLOAT_MAX is considered infinite. PHP has the following functions to check if a numeric value is finite or infinite: is_finite() is_infinite() However, the PHP var_dump() function returns the data type and value: Example Check if a numeric value is finite or infinite: PHP NaN NaN stands for Not a Number. NaN is used for impossible mathematical operations. PHP has the following functions to check if a value is not a number: is_nan() However, the PHP var_dump() function returns the data type and value: Example Invalid calculation will return a NaN value: PHP Numerical Strings The PHP is_numeric() function can be used to find whether a variable is numeric. The function returns true if the variable is a number or a numeric string, false otherwise. Example Check if the variable is numeric: Note: From PHP 7.0: The is_numeric() function will return FALSE for numeric strings in hexadecimal form (e.g. 0xf4c3b00c), as they are no longer considered as numeric strings. PHP Casting Strings and Floats to Integers Sometimes you need to cast a numerical value into another data type. The (int), (integer), or intval() function are often used to convert a value to an integer. Example Cast float and string to integer: "; // Cast string to int $x = "23465.768"; $int_cast = (int)$x; echo $int_cast; ?> PHP Math PHP has a set of math functions that allows you to perform mathematical tasks on numbers. PHP pi() Function The pi() function returns the value of PI: Example PHP min() and max() Functions The min() and max() functions can be used to find the lowest or highest value in a list of arguments: Example PHP abs() Function The abs() function returns the absolute (positive) value of a number: Example PHP sqrt() Function The sqrt() function returns the square root of a number: Example PHP round() Function The round() function rounds a floating-point number to its nearest integer: Example Random Numbers The rand() function generates a random number: Example To get more control over the random number, you can add the optional min and max parameters to specify the lowest integer and the highest integer to be returned. For example, if you want a random integer between 10 and 100 (inclusive), use rand(10, 100): Example PHP Constants Constants are like variables except that once they are defined they cannot be changed or undefined. PHP Constants A constant is an identifier (name) for a simple value. The value cannot be changed during the script. A valid constant name starts with a letter or underscore (no $ sign before the constant name). Note: Unlike variables, constants are automatically global across the entire script. Create a PHP Constant To create a constant, use the define() function. Syntax define(name, value, case-insensitive) Parameters: name: Specifies the name of the constant value: Specifies the value of the constant case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false Example Create a constant with a case-sensitive name: Example Create a constant with a case-insensitive name: PHP Constant Arrays In PHP7, you can create an Array constant using the define() function. Example Create an Array constant: Constants are Global Constants are automatically global and can be used across the entire script. Example This example uses a constant inside a function, even if it is defined outside the function: PHP Operators PHP Operators Operators are used to perform operations on variables and values. PHP divides the operators in the following groups: Arithmetic operators Assignment operators Comparison operators Increment/Decrement operators Logical operators String operators Array operators Conditional assignment operators PHP Arithmetic Operators The PHP arithmetic operators are used with numeric values to perform common arithmetical operations, such as addition, subtraction, multiplication etc. Operator Name Example Result Show it + Addition $x + $y Sum of $x and $y - Subtraction $x - $y Difference of $x and $y * Multiplication $x * $y Product of $x and $y / Division $x / $y Quotient of $x and $y % Modulus $x % $y Remainder of $x divided by $y ** Exponentiation $x ** $y Result of raising $x to the $y'th power PHP Assignment Operators The PHP assignment operators are used with numeric values to write a value to a variable. The basic assignment operator in PHP is "=". It means that the left operand gets set to the value of the assignment expression on the right. Assignment Same as... Description Show it x = y x = y The left operand gets set to the value of the expression on the right x += y x = x + y Addition x -= y x = x - y Subtraction x *= y x = x * y Multiplication x /= y x = x / y Division x %= y x = x % y Modulus PHP Comparison Operators The PHP comparison operators are used to compare two values (number or string): Operator Name Example Result Show it == Equal $x == $y Returns true if $x is equal to $y === Identical $x === $y Returns true if $x is equal to $y, and they are of the same type != Not equal $x != $y Returns true if $x is not equal to $y <> Not equal $x <> $y Returns true if $x is not equal to $y !== Not identical $x !== $y Returns true if $x is not equal to $y, or they are not of the same type > Greater than $x > $y Returns true if $x is greater than $y < Less than $x < $y Returns true if $x is less than $y >= Greater than or equal to $x >= $y Returns true if $x is greater than or equal to $y <= Less than or equal to $x <= $y Returns true if $x is less than or equal to $y <=> Spaceship $x <=> $y Returns an integer less than, equal to, or greater than zero, depending on if $x is less than, equal to, or greater than $y. Introduced in PHP 7. PHP Increment / Decrement Operators The PHP increment operators are used to increment a variable's value. The PHP decrement operators are used to decrement a variable's value. Operator Name Description Show it ++$x Pre-increment Increments $x by one, then returns $x $x++ Post-increment Returns $x, then increments $x by one --$x Pre-decrement Decrements $x by one, then returns $x $x-- Post-decrement Returns $x, then decrements $x by one PHP Logical Operators The PHP logical operators are used to combine conditional statements. Operator Name Example Result Show it and And $x and $y True if both $x and $y are true or Or $x or $y True if either $x or $y is true xor Xor $x xor $y True if either $x or $y is true, but not both && And $x && $y True if both $x and $y are true || Or $x || $y True if either $x or $y is true ! Not !$x True if $x is not true PHP String Operators PHP has two operators that are specially designed for strings. Operator Name Example Result Show it . Concatenation $txt1 . $txt2 Concatenation of $txt1 and $txt2 .= Concatenation assignment $txt1 .= $txt2 Appends $txt2 to $txt1 PHP Array Operators The PHP array operators are used to compare arrays. Operator Name Example Result Show it + Union $x + $y Union of $x and $y == Equality $x == $y Returns true if $x and $y have the same key/value pairs === Identity $x === $y Returns true if $x and $y have the same key/value pairs in the same order and of the same types != Inequality $x != $y Returns true if $x is not equal to $y <> Inequality $x <> $y Returns true if $x is not equal to $y !== Non-identity $x !== $y Returns true if $x is not identical to $y PHP Conditional Assignment Operators The PHP conditional assignment operators are used to set a value depending on conditions: Operator Name Example Result Show it ?: Ternary $x = expr1 ? expr2 : expr3 Returns the value of $x. The value of $x is expr2 if expr1 = TRUE. The value of $x is expr3 if expr1 = FALSE ?? Null coalescing $x = expr1 ?? expr2 Returns the value of $x. The value of $x is expr1 if expr1 exists, and is not NULL. If expr1 does not exist, or is NULL, the value of $x is expr2. Introduced in PHP 7
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