php - Deleting specific data from a text document using fwrite? -

i writing "unfriend" script mini social network, unfriend action needs remove id called: $user friend list , id called: $my_id. have made scripts add user id's each users files not sure how delete this?

my friend_list file: 1,2,3 // user 1

their friend_list file: 1,2,3 // user 3

i use add each id text file:

if($action === 'accept'){     mysql_query("delete `friend_req` `from`='$user' , `to`='$my_id'");      $fp = fopen($user_data['friend_list'], 'a');     fwrite($fp, ",".$user."");     fclose($fp);      $their_id = friend_list_from_user_id($user);     $fp = fopen($their_id, 'a');     fwrite($fp, ",".$my_id."");     fclose($fp); } 

but remove $my_id friend_list , $userid friend_list i'm thinking need use isn't working:

if($action === 'unfriend'){     $fp = fopen($user_data['friend_list'], 'a');     unset($user);     fclose($fp);      $their_id = friend_list_from_user_id($user);     unset($my_id);     fclose($fp); } 

but doesn't seem work, should delete specified usernames respective file?

oh, , also, may/may not of use:

$myfile = $file; $fh = fopen($myfile, 'r'); $thedata = fgets($fh); fclose($fh);  $friend = explode(',', $thedata);  for($i=0; $i < count($friend); $i++){     if($i >= 0)     {         if($friend[$i] == $user_id) {         $their_user_id = $user_id;     } } 

to solve issue like:

//get contents of file $contents = file_get_contents($user_data['friend_list']); $contents = str_replace(",".$friend_id, "", $contents); //remove friend's id  //open file again , rewrite whole thing new contents without id $fp = fopen($user_data['friend_list'], 'w+'); fwrite($fp, $contents); fclose($fp);