PHP » Operators » <<

Syntax:
expression1 << expression2
expression1
Number to shift.
expression2
Number of steps to shift it.

Shift left.

This operator shifts a binary number a number of steps to the left.

Examples

Code:
<?php

$a = 11;
$b = $a << 1;

printf("%b << 1 = %b", $a, $b);

?>
Output:
1011 << 1 = 10110
Explanation:

A number is shifted one step to the left.