Calculate the variable name for simpler variables and use that name to access the value of that variable.

 
<?php
$a0 = 'This';
$a1 = 'is';
$a2 = 'a';
$a3 = 'test';

for ($i = 0; $i < 4; $i++) {
  $var = "a$i";
  echo "${$var} ";
}
?>

1.	PHP Variable Examples
2.	PHP Superglobal Arrays
3.	PHP 5 variable functionality.
4.	A properly set-up PHP variable
5.	Automatic Type Conversion
6.	Operating on variables
7.	valid statements
8.	Numbers
9.	Numeric Data Types
10.	Valid and invalid variable names

Calculate the variable name for simpler variables and use that name to access the value of that variable. : Variables « Language Basics « PHP