Description:
------------
This script simply augments an array by duplicating its first element a parameter number of time, then displays count of the array and memory usage.

$ php finout.php 65536
count:65536/2968016 bytes

$ php finout.php 65537
count:65537/3230200 bytes
*** glibc detected *** double free or corruption (!prev): 0x0923ce30 ***
Aborted

When count reaches 65537 glibc issues this "post-mortem" message

If instead of $arr[] = $arr[0]; I use $arr[] = 'x'; this message does not come.

Reproduce code:
---------------
<?php
$loop = isset($_SERVER['argv'][1]) ? $_SERVER['argv'][1]+0 : 1000;
error_reporting(E_ALL);
$arr = array ('x') ;
while (--$loop) {
    $arr[] = $arr[0];
}
echo 'count:'.count($arr).'/'.memory_get_usage() . " bytes\n";
?>