Unexplained Issue Using Regex

Hi lista, I have been trying to figure this out for the last couple of hours but I'm lack of luck. Take a look at these regex's, the string that was inputed into the preg_replace (using Uis modificators) and the results: (the lists have correspondence to each other) ORIGINAL STRING ---- http://www.zshare.net/video/541070871c7a8d9c http://www.guba.com/watch/2000821351 http://www.veoh.com/videos/v4609719YfsCFpf REGEX USED (with Uis modificators) ---- http:\/\/(www\.|)zshare\.net\/video\/([^\/]+) $3 http:\/\/(www\.|)guba\.com\/watch\/([0-9]+) $3 http:\/\/(www\.|)veoh\.com\/videos\/([^\/]+) THE RETURNED STRING ---- 41070871c7a8d9c 000821351 4609719YfsCFpf If you will go through this carefully you will notice that the first character of each matching group is being deleted. The regex's and the replacements string are being fetched from the database (mysql) and goes straight to the preg_replace function with the original string. I have no idea why this happens. I'm looking forward for your opinions and suggestions. Regards, Nitsan