PHP Explode VS Unserialize (Who's Faster?)

gistfile1.php

<?php
//This is the list of elements. There are 500 items in this array.

/* From PHP.net  */
function convert($size){
    $unit=array('b','kb','mb','gb','tb','pb');
    return @round($size/pow(1024,($i=floor(log($size,1024)))),2).' '.$unit[$i];
 }

	
	$start1 = microtime(true);
	$start1mem = memory_get_usage();
	$explodeThisArray = explode($explodeThis,",");
	echo "Explode took ".(microtime(true)-$start1)." Seconds<br/>";
	echo "Explode used ".convert(memory_get_usage()-$start1mem)." of memory<br/><br/>"; 
	//empty it from memory
	$explodeThisArray = array();
	
	
	$start = microtime(true);
	$startmem = memory_get_usage();
	$unserializeThis = unserialize($unserializeThis);
	echo "Unserialize took ".(microtime(true)-$start)." Seconds<br/>";
	echo "Unserialize used ".convert(memory_get_usage()-$startmem)." of memory<br/><br/>"; 
	//empty it from memory
	$unserializeThis = array();
	
	
	$start3 = microtime(true);
	$start3mem = memory_get_usage();
	$jsonDecodeThis = json_decode($jsonDecodeThis);
	echo "JSON Decode took ".(microtime(true)-$start3)." Seconds<br/>";
	echo "JSON Decode used ".convert(memory_get_usage()-$start3mem)." of memory<br/><br/>"; 
	//empty it from memory
	$jsonDecodeThis = array();
	

$explodeThisArray = explode($explodeThis,",");

array explode ( string $delimiter , string $string [, int $limit ] )

delimiter must be first parameter