Description:
------------
The is_array() function does not takes it's argument by reference, but copies it. When it takes a large array as an argument and it is called this way many times (for example in a "for" cycle) then it can take a huge time to run beacause of large amount of memory copies.

The same problem probably exists at other array related functions.

In PHP 5.3 and earlier you cound use is_array(&$array) to mitigate the performance bottleneck. Since call-time pass-by-reference was removed in PHP 5.4 there is no way to do a workaround anymore.

Test script:
---------------
<?php

function delta($prefix, $t1) {
        $t2 = microtime(true);
        printf("%s %0.6f\n", $prefix, ($t2 - $t1) * 1000);
}

function &genarray() {
        $a = array();
        for($i = 0; $i < 10000; $i++) {
                $a[] = $i;
        }
        return($a);
}

function noref(&$a) {
        for($i = 0; $i < 10000; $i++) {
                is_array($a);
        }
}

function byref(&$a) {
        for($i = 0; $i < 10000; $i++) {
                is_array(&$a);
        }
}

$a = &genarray();
$t1 = microtime(true);
noref($a);
delta("NoRef:", $t1);

$t3 = microtime(true);
byref($a);
delta("ByRef:", $t3);

?>


Expected result:
----------------
I expected that NoRef timing be (almost) equal to ByRef timing.

Actual result:
--------------
NoRef: 9246.673107
ByRef: 1.910925

NoRef is ~5000 times slower than ByRef.