<?php

$list1 = file( "list1.txt" );
$list2 = file( "list2.txt" );

for( $i=0; $i<count($list2); $i++ ){

if( in_array( $list2[$i], $list1 ) ){ /* do nothing */ } else { $new_array[] = $list2[$i]; }

}

echo "<pre>";
print_r( $new_array );
echo "</pre>";

?>