regex: detect internal domains in urls

regex.php

<?php
$allow = array
(
    '*.eitb.*',
    'tortolika'
);

$urls = array
(
    'www.eitb.eus/asjdhjashdjahjkdhajkhdjk/',
    'http://www.eitb.eus/asjdhjashdjahjkdhajkhdjk/',
    'http://pre.eitb.eus/',
    'http://tortolika/',
    'tortolika/adasdasdass',
    'http://www.google.es',
    'www.google.es'
);

$z = array();
foreach($urls as $url)
{
    foreach($allow as $a)
    {
        $b = preg_replace("/\./", '\.', $a);
        $b = preg_replace("/\*/", '[^\s]+', $a);
        $b = "^(https?:\/\/|){$b}";
        if(preg_match("/$b/i", $url))
            $z[] = $url;
    }
}

print_r($z);

Output:
Array
(
[0] => www.eitb.eus/asjdhjashdjahjkdhajkhdjk/
[1] => http://www.eitb.eus/asjdhjashdjahjkdhajkhdjk/
[2] => http://pre.eitb.eus/
[3] => http://tortolika/
[4] => tortolika/adasdasdass
)