Curriculum

PHP Variables

In this tutorial, you will learn how to use PHP variables to store data in program.

Define a Variable

A variable can hold any type of value, such as a string, a number, an array, or an object.

A variable is given a name and is given a value. The following syntax is used to define a variable:

$variable_name = value;

The following rules must be followed when defining a variable:

The variable name must begin with the letter $. After the dollar symbol ($), the first character must be a letter (a-z) or an underscore ( ).
Underscores, letters, or digits can make up the remaining characters.
Variables in PHP are case-sensitive. It means that the variables $message and $Message are completely different.

The variable $title is defined in the following example:

<?php
$title = "PHP is awesome!";

The echo construct is used to display the values of variables on a webpage. Consider the following scenario:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>PHP Variables</title>
</head>
<body>
    <?php
        $title = 'PHP is awesome!';
    ?>
    <h1><?php echo $title; ?></h1>
</body>
</html>

You’ll notice the following message if you open the page:

PHP is awesome!

Use the following syntax to show the value of a variable on a page in a more compact manner:

<?= $variable_name ?>

The value of the $title variable in the header, for example, is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>PHP Variables</title>
</head>
<body>
    <?php
        $title = 'PHP is awesome!';
    ?>
    
    <h1><?= $title; ?></h1>
</body>
</html>

When PHP and HTML are mixed together, the code becomes unmaintainable, especially as the application grows. Different the code into separate files to avoid this. Consider the following scenario:

The logic for defining and assigning values to variables is stored in index.php.

index.view.php – this file contains the code for displaying the variables.
To include the code from index.view.php in the index.php file, use the require construct.
The contents of the index.view.php file are as follows:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>PHP Variables</title>
</head>
<body>
    <h1><?= $title ?></h1>
</body>
</html>

The contents of the index.php file are shown below:

<?php

$title = 'PHP is awesome!';
require 'index.view.php';

You’ll get the same result if you open the index.php file in a web browser.

This allows you to segregate the logic code from the code responsible for displaying the file. In programming, this is referred to as the separation of concerns (SoC).

PHP

PHP Variables

Define a Variable

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