href値の内容を取得する

Since parsing HTML using regular expressions is a Bad Thing™, I suggest a less crude method:

$dom = new DomDocument;
$dom->loadHTML($pageContent);

$elements = $dom->getElementsByTagName('a');

for ($n = 0; $n < $elements->length; $n++) {
    $item = $elements->item($n);
    $href = $item->getAttribute('href');
   //here's your href attribute
}