eregi vs strpos

[sabret00the]

PHP Code:

        while(!feof($newfile))
        {
            $duplicate = fgets($newfile, 255);
            // is email address submitted already in the file?
            $dupe = eregi($email, $duplicate);
            if($dupe == TRUE)
            {
                $content = "Our records show that this email address is already registered";
                fclose($newfile);
                //exit;
                die("$front\n$content\n$back");
            }
        } 


that works fine but

PHP Code:

        while(!feof($newfile))
        {
            $duplicate = fgets($newfile, 255);
            // is email address submitted already in the file?
            $dupe = strpos($email, $duplicate);
            if($dupe == TRUE)
            {
                $content = "Our records show that this email address is already registered";
                fclose($newfile);
                //exit;
                die("$front\n$content\n$back");
            }
        } 


don't, how come?