<?php
    $a = 3;     // assigns value of 3 to variable $a
    $a = ($b = 4) + 5;  //$a equals to 9 while $b is set to 4
    $b = "Robert";  // A string is assigned to variable $b
    $a += 5;    // this is the same as $a = $a + 5;
    $b = &$a;   // $b is a reference to $a
    $a -= $b;   // this is the same as $a = $a - $b
    $a *= $b;   // this is the same as $a = $a * $b
    $a /= $b;   // this is the same as $a = $a / $b
    $a %= $b;   // $a is modulus of $b
?>