Why there isn't an "ftp_get_contents" function, I don't know. It takes a little work to emulate one, but it's doable.
<?php
function ftp_get_contents($ftp_stream, $remote_file, $mode, $resume_pos=null){
    $pipes=stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, STREAM_IPPROTO_IP);
    if($pipes===false) return false;
    if(!stream_set_blocking($pipes[1], 0)){
        fclose($pipes[0]); fclose($pipes[1]);
        return false;
    }
    $fail=false;
    $data='';
    if(is_null($resume_pos)){
        $ret=ftp_nb_fget($ftp_stream, $pipes[0], $remote_file, $mode);
    } else {
        $ret=ftp_nb_fget($ftp_stream, $pipes[0], $remote_file, $mode, $resume_pos);
    }
    while($ret==FTP_MOREDATA){
        while(!$fail && !feof($pipes[1])){
            $r=fread($pipes[1], 8192);
            if($r==='') break;
            if($r===false){ $fail=true; break; }
            $data.=$r;
        }
        $ret=ftp_nb_continue($ftp_stream);
    }
    while(!$fail && !feof($pipes[1])){
        $r=fread($pipes[1], 8192);
        if($r==='') break;
        if($r===false){ $fail=true; break; }
        $data.=$r;
    }
    fclose($pipes[0]); fclose($pipes[1]);
    if($fail || $ret!=FTP_FINISHED) return false;
    return $data;
}
?>
Something similar would work to write a ftp_put_contents function, too.