<?php

$my_array = array('b' => 'something');

$err = error_reporting(0);

$start1 = time();

for ($i = 0; $i < 1000000; $i++) {
    $my_array['a'];
    $my_array['b'];
}

echo (time() - $start1), " seconds\n";

error_reporting($err);

$start2 = time();

for ($i = 0; $i < 1000000; $i++) {
    @$my_array['a'];
    @$my_array['b'];
}

echo (time() - $start2), " seconds\n";

$start3 = time();

for ($i = 0; $i < 1000000; $i++) {
    if (isset($my_array['a'])) {
        $my_array['a'];
    }
    if (isset($my_array['b'])) {
        @$my_array['b'];
    }
}

echo (time() - $start3), " seconds\n";