Manipulating a text file

Hello php-general, I need to be able to add and delete to a text file that look like this. I only need to manipulate the part after site:x:503: site1:x:503:tester1,tester6 site2:x:504: site3:x:505: site4:x:506: site5:x:507: site6:x:508: site7:x:509:tester2,tester3,tester4 site8:x:510: site9:x:511: I can get to this value by using this code below. But I have know Idea on how to go about this. I want to be able to add to this list and delete from the list. Example I would like to remove tester3 from site7 and then I would like to add tester10 to site4. This should give you an idea of what I am trying to do. I have asked this question before but have never received an answer that I could understand. $groups= file("group"); $number_in_group = count($groups); for( $i = 0; $i < $number_in_group; $i++){ $group = explode(":",$groups[$i]); $group[0]; $group[3]; //this is the group I what to be able to change but referenced by group[0] I need to be able to add to and delete from this group and then save it to a file } -- Best regards, Richard mailto:rdkurth@starband.net