A variable is a name for some piece of information.

In PHP, variables start with a $ (dollar sign) symbol.

Use the assignment operator (equals sign, =) to assign a value to a variable. Example:

<?php
$txt="Hello World!";
print $txt;   // outputs "Hello World!" (without quotes)
?>

The variable $txt is assigned the value “Hello World!”.

This type of data — some arbitrary text inside quote marks — is known as a string in computer programming.

Example using numbers:

<?php
$a=1;
$b=2;
print $a + $b;   // outputs 3
?>

Be careful not to confuse the assignment opertor (equals sign, =) with the equality operator (double equals sign, ==).

Rules for naming variables

  • A variable name must start with a letter or an underscore “_”
  • A variable name can only contain alpha-numeric characters and underscores (a-z, A-Z, 0-9, and _ )
  • A variable name must not contain spaces. If a variable name is more than one word, it should be separated with an underscore ($my_string), or with capitalization ($myString)