- preg_match: documentation ( source)
<?php
$tracking = '1Z0ER5190360727519';
if(preg_match("/\b(1Z ?[0-9A-Z]{3} ?[0-9A-Z]{3} ?[0-9A-Z]{2} ?[0-9A-Z]{4} ?[0-9A-Z]{3} ?[0-9A-Z]|[\dT]\d\d\d ?\d\d\d\d ?\d\d\d)\b/i", $tracking)==1){print "http://wwwapps.ups.com/WebTracking/track?track=yes&trackNums=".$tracking;}
if(preg_match("/\b((96\d\d\d\d\d ?\d\d\d\d|96\d\d) ?\d\d\d\d ?d\d\d\d( ?\d\d\d)?)\b/i", $tracking)==1){print "https://www.fedex.com/fedextrack/?tracknumbers=".$tracking;}
if(preg_match("/\b(91\d\d ?\d\d\d\d ?\d\d\d\d ?\d\d\d\d ?\d\d\d\d ?\d\d|91\d\d ?\d\d\d\d ?\d\d\d\d ?\d\d\d\d ?\d\d\d\d)\b/i", $tracking)==1){print "https://tools.usps.com/go/TrackConfirmAction.action?tLabels=".$tracking;}