PHP micro optimizations for is_null vs isset vs === NULL

<?php

/**

By Pablo Pazos @ppazos

Test result:
isset 0.69305992126465
is_null 2.0065321922302
== NULL 0.79327797889709
=== NULL 0.76104307174683
!= NULL 0.79441618919373
!== NULL 0.69468784332275
*/

$counter = 5000000;
$name    = 'henry';
$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    isset($name);
}
$end   = microtime(true);
echo "isset ", $end - $start, "<br/>";


$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    is_null($name);
}
$end   = microtime(true);
echo "is_null ", $end - $start, "<br/>";


$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    $name == NULL;
}
$end   = microtime(true);
echo "== NULL ", $end - $start, "<br/>";


$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    $name === NULL;
}
$end   = microtime(true);
echo "=== NULL ", $end - $start, "<br/>";


$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    $name != NULL;
}
$end   = microtime(true);
echo "!= NULL ", $end - $start, "<br/>";


$start   = microtime(true);
for($i=0; $i<$counter; $i++) {
    $name !== NULL;
}
$end   = microtime(true);
echo "!== NULL ", $end - $start, "<br/>";

?>