PHP Variables

Variables are pieces of information stored in the computer's memory.

Variables are used to store information and retrieve them when needed. They can be labeled with a meaningful name to be understood easily by the readers and ourselves.

The data stored in variables can be changed.

What can we do with variables?

We can think a variable as a box.

A variable can have a name
A variable can hold a value
A variable's value can be updated

See the following image.

Variables are like boxes

PHP Variable Naming

As a box can be labeled with a name, similarly, a variable can be (actually, should be) labeled with a name. In PHP, there are certain rules to follow when naming a variable.

Rules for PHP Variables

The $ identifier should be added in front of the name of the variable.
A variable name must start with a letter or underscore.
A variable name cannot start with a number.
A variable name cannot be $this. ($this is a special variable which cannot be assigned)
A variable name can contain letters, numbers, and characters between 127-255 ASCII after the first character.
Variable names are case sensitive.

PHP Variable naming


<?php

$name = 'Hyvor'; 	// valid
$_name = 'Hyvor';	// valid - starts with an underscore
$näme = 'Hyvor';  // valid - 'ä' is (Extended) ASCII 228

$1name = 'Hyvor';	// invalid - cannot start with a number
$this = 'Hyvor'; 	// invalid - cannot assign value to $this

Note that the variable names are case-sensitive. $name and $Name are two different variables.

Tip: Always use a meaningful name for a variable.

PHP Declaring Variables

In programming, creating a variable is called declaring. But, in PHP, unlike other programming languages, there is no keyword to declare a variable.

Variables are declared when you assign a value to them

Unlike other programming languages, you do not have to define data types for variables. (Programming languages like this is called loosely typed languages)

Note: Strings should be wrapped with " (double-quotes) or ' (single-quotes). (We will learn more about quoting in PHP Output tutorial.)

When declaring a variable,

The variable name must be on the left.
The = sign as the assignment operator.
Next, the value to be assigned.
Finally, ; sign to say the statement is finished.

PHP Variable Assignment

PHP Declaring Variables Example


<?php
$month = "May";
$day = 22;

After running this part of the script,

The text value, May is stored in the $month variable. (Note that " - double-quotes are not saved)
The numeric value, 22 is stored in the $day variable.

PHP Reassigning Values to Variables

A variable stores the value of its most recent assignment.

The output of the below code is "World" because it is the value of the last assignment of $text.

PHP Reassigning Variables Example


<?php
$text = 'Hello';
$text = 'World';

echo $text;

Run Example ››

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