need a simply preg_match, which will find \"c.aspx\" (without quotes) in the content if it finds, it will return the whole url. As a example
$content = \'
You use DOM to parse HTML, not regex. You can use regex to parse the attribute value though.
Edit: updated example so it checks for c.aspx.
$content = '<div>[4]<a href="/m/c.aspx?mt=01_9310ba801f1255e02e411d8a7ed53ef95235165ee4fb0226f9644d439c11039f%7c8acc31aea5ad3998&n=783622212">New message</a>
<a href="#bar">foo</a>
<br/>';
$dom = new DOMDocument();
$dom->loadHTML($content);
$anchors = $dom->getElementsByTagName('a');
if ( count($anchors->length) > 0 ) {
foreach ( $anchors as $anchor ) {
if ( $anchor->hasAttribute('href') ) {
$link = $anchor->getAttribute('href');
if ( strpos( $link, 'c.aspx') ) {
echo $link;
}
}
}
}
If you want to find any quoted string with c.aspx in it:
/"[^"]*c\.aspx[^"]*"|'[^']*c\.aspx[^']*'/
But really, for parsing most HTML you'd be better off with some sort of DOM parser so that you can be sure what you're matching is really an href.