<?php
$file_a=dirname(__FILE__).'/Dateia.txt';
$file_b=dirname(__FILE__).'/Dateib.txt';
// get content from file a
$content_a=file($file_a);
$content_b=file($file_b);
// delete items from content b
foreach(array_keys($content_b) as $key)
if(in_array($content_b[$key], $content_a))
unset($content_b[$key]);
// write new data in file_b
$handle=fopen($file_b, 'w');
fputs(implode("\n", $content_b));
fclose($handle);
?>