Casting vs intval()

gistfile1.php

function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

function a()
{
    $a = array();
    $test = @intval($a['test']);
    return $test;
}

function b()
{
    $a = array();
    if (isset($a['test'])) {
        return (int) $a['test'];
    } else {
        return 0;
    }
}
$loop = 100000;
$time_start = microtime_float();
for ($i = 0; $i < $loop; $i++) {
    a();
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo 'intval(): ' . $time ;
echo '<br />';

$time_start = microtime_float();
for ($i = 0; $i < $loop; $i++) {
    b();
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo 'Casting: ' . $time;