Search & replace text

Hello all. I am trying to search through a text file on my server to replace the user email. I can open the file and read it, but cannot get it to "find" the actual string and replace it. Can someone look over my code and see what the problem is? I am afraid that ereg is not my strongest point. Also, at what point should I start writing the file out? Wouldn't there be a permissions error if I was reading and writing at the same time? Thanks CDitty $oldemail = "email1@mydomain.com"; $newemail = "email2@mydomain.com"; $user = "cditty"; $file = fopen("/path/to/the/user/file/$user.dat", "r"); if(!$file){

        echo "<p>Unable to open remote file.\n";
        exit;

}else{

    echo "Success<br>";

} while (!feof($file)) {

        $line = fgets($file, 255);
        if(eregi($oldemail, $line, $out)) {
                str_replace($oldemail, $newemail, $line);
        }

echo $line . "<BR>"; } fclose($file)