PHP benchmark performance: `strlen` vs `mb_strlen`

gistfile1.php

<?php

$iterations = 10000;
$str = 'The speed of calculating the length of this string will be performed.';

function a($s)
{
	$l = strlen($s);
}

function b($s)
{
	$l = mb_strlen($s);
}


$a_time = 0;
$i = 0;
$a_start = microtime(true);
while ($i <= $iterations) {
	a($str);
	$i++;
}
$a_end = microtime(true);

$b_time = 0;
$i = 0;
$b_start = microtime(true);
while ($i <= $iterations) {
	b($str);
	$i++;
}
$b_end = microtime(true);

echo 'strlen: ' . ($a_end - $a_start) . '<br />';
echo 'mb_strlen: ' . ($b_end - $b_start);