$re = '/@if(?:\s+|)\(([\s\S]*?)\)([\s\S]*?)+@endif/i';
$str = '<div class="wrapper">
<p>Parágrafo fora dos ifs.</p>
@if (true)
<div>Oi?</div>
@if (false)
<span>Não devo ser renderizado</span>
@endif
@endif
<p>Estou entre os if\'s</p>
@if (true)
<div>estou em outro if</div>
@endif
</div>';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php