- var_dump: documentation ( source)
<?php
$myArray = array(
"0" => array("0" => "test1", "1" => "test2"),
"1" => array("0" => "test3", "1" => "test4"));
$myArray["45"] = $myArray["0"];
unset($myArray["0"]);
$myArray["51"] = $myArray["1"];
unset($myArray["1"]);
var_dump($myArray);