Regex strip some content : <p>I have code which contains 3 or more [iframe] shortcode, and I only want to keep one with specific url (specific.com in this example)</p>

<pre><code> $content = '[iframe src="https://specific.com/player/embed_player.php?vid=123"][/iframe]&lt;strong&gt;Dailymotion.com&lt;/strong&gt;&lt;br /&gt;[iframe src="//dailymotion.com/embed/video/k4oXSHJdKT8QsBrqBI5?logo=0&amp;amp;info=0&amp;amp;hideInfos=1"][/iframe]&lt;strong&gt;Some Website&lt;/strong&gt;&lt;br /&gt;[iframe src="//site.com/embed/video/123"][/iframe]';
</code></pre>

<p>The content data sequence of [iframe] shortcodes can be different, however I want the following output only..</p>

<pre><code> [iframe src="https://specific.com/player/embed_player.php?vid=123"][/iframe]
</code></pre>
