Preg_match problem

[sastro]

here the script

<?php
$a='dir/5_cat/big-dog.html
dir/0_cat/wild-dog.html
dir/1_cat/expensive-dog.html
dir/3_cat/expensive-cat.html';

$b='dir/1_cat/expensive-dog.html';
$th=str_replace(array('.','/'),array('\.','\/'),$b);
if(preg_match('/'.$th.'/',$a)){
echo 'found';
}else{
echo 'not found';
}
?>

 

It works if

$b='dir/1_cat/expensive-dog.html';

but result still found with

$b='dir/1_cat/expensive-dog.htm';

 

Please help

[sastro]

Wrong question... Sory, it my false.