php处理俩个文本的效率问题

<?php/*==> 1.txt <==a:123b:1333c:333==> 2.txt <==a:3333aa:3433c:323dfa==> result.txt <==a:123:3333c:333:323dfa*/$file_1 = "1.txt";$file_2 = "2.txt";$f = fopen("$file_1", 'r') or die("Cann't Open the file.");while (!(feof($f))) {        $line = explode(':', trim(fgets($f)));        $f2 = fopen("$file_2", 'r') or die("Cann't Open the file.");        while (!(feof($f2))) {                $line2 = explode(':', trim(fgets($f2)));                if ($line[0] == $line2[0]) {                        $line[] = $line2[1];                        $aaaa = implode(":",$line);                        $output_file = fopen("./result.txt", 'a');                        echo "$aaaa\n";                        fwrite($output_file, "$aaaa\n");                        fclose($output_file);                }        }}?>