<?php

/**
 * Filters out valid mac characters to return a uniform MAC format
 * @param  String $mac The raw string expression
 * @return String      The filtered/formatted MAC address
 */
function format_mac_address($mac)
{
	if(!$mac || $mac == "")
	{
		// If no MAC was passed, return;
		return null;
	}
	preg_match_all('/[0-9a-fA-F]/', $mac, $matches);
	if(!$matches || sizeof($matches[0]) != 12)
	{
		// If the number of filtered characters is not 12, return for invalid mac;
		return null;
	}
	$filteredMac = "";
	foreach($matches[0] as $match)
	{
		// Add each character into a string and capitalize the alphas
		$filteredMac .= strtoupper($match[0]);
	}
	// Split the characters into segments of 2
	$macSegmenets = str_split($filteredMac,2);
	// Glue the segments together with a colon
	$finalMac = implode(":",$macSegmenets);
	return $finalMac;
}