replacing just one word in a text file

[Spud_Nic]

Hi

I've been able to read and write to text files ok in the past, but this one is bugging me as I can't figure this out.

if ($userinformationresult == "correct") {
 $fileurl = "incs/users.txt";
 $fd = fopen ("$fileurl", "r+");
   while (!feof ($fd)) {
      $buffer = fgets($fd, 1024);
      $buffer = eregi_replace($oldpassword, $newpassword, $buffer);
       //echo $buffer; this will echo the data fine, and as I want it

  $writesuccess = fwrite($fd, $buffer);
}	
fclose ($fd);

All I want to do, is open a text file, search for one word, and replace it and then save the text file again.
I'm not sure if its the mode? r+ seems right to me!
the problem is definately the fwrite line, but I've been looking in the manual for ages with no luck!

Anyone see what is wrong?

cheers

[devinemke]

$search = 'Search for this';
$replace = 'Replace it with this';

$contents = file_get_contents ('users.txt');
$contents = str_replace ($search, $replace, $contents);

$handle = fopen ('users.txt', 'w');
fwrite ($handle, $contents);
fclose ($handle);