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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 consider a variable like 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 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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