PHP 5 Variables

 

Creating (Declaring) PHP Variables

In PHP, a variable starts with the $ sign, followed by the name of the variable

Example

<?php
$txt = "Hello world!";
$x = 5;
$y = 10.5;
?>

 

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)

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

<?php
$txt = "W3Schools.com";
echo "I love $txt!";
?>

 

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 converts the variable to the correct data type, depending on its value.
In other languages such as C, C++, and Java, the programmer must declare the name and type of the variable before using it.

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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

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Global and Local Scope

A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:

Example

<?php
$x = 5; // global scope

function myTest() {
    // using x inside this function will generate an error
    echo "<p>Variable x inside function is: $x</p>";
}
myTest();

echo "<p>Variable x outside function is: $x</p>";
?>