用于扫描带有另一个标签内的标签的子串的正则表达式

I have a string that may contain substring:

<h1 style="margin: 0; padding: 0" class="title_big">Item title <span style="white-space: nowrap"> (5 entries)</span></h1>

or just

<h1 style="margin: 0; padding: 0" class="title_big">Item title</h1>

(with no internal SPAN) Now I can't figure out how to compose regexp. Currently using such one:

$pat='/<h1 style="margin: 0; padding: 0" class="title_big">([^>]*)<\/h1>/si';

but of course it doesn't return match for substring with internal SPAN

If you set $pat to this instead it should work:

$pat = '/<h1 style="margin: 0; padding: 0" class="title_big">(.*?)<\/h1>/uim';