<iframe width="560" height="315" src="//www.youtube.com/embed/UPk1B1bxUPg" frameborder="0" allowfullscreen></iframe>
<iframe width="560" height="315" src="//www.youtube.com/embed/UPk1B1bxUPg/?wmode=transparent" frameborder="0" allowfullscreen></iframe>
$str = '<iframe width="560" height="315" src="//www.youtube.com/embed/UPk1B1bxUPg" frameborder="0" allowfullscreen></iframe>';
$dom = new DOMDocument();
$dom->loadHTML($str);
foreach($dom->getElementsByTagName('iframe') as $iframe) {
$src = $iframe->getAttribute('src');
$src .= '?wmode=transparent'; // use a regex for better results
$iframe->setAttribute('src', $src);
}
echo $dom->saveHTML();
<?php
$videoEmbedCode = '<iframe width="560" height="315" src="//www.youtube.com/embed/UPk1B1bxUPg" frameborder="0" allowfullscreen></iframe>';
$appendString = '/?wmode=transparent';
/* Youtube video sticky menu overlap fix */
$searchStartLen = strpos($videoEmbedCode, 'youtube');
$searchEndLen = strpos($videoEmbedCode, '"', $searchStartLen);
$newVideoEmbedCode = substr_replace($videoEmbedCode, $appendString, $searchEndLen, 0);
print $newVideoEmbedCode;
?>
$doc = new DOMDocument();
$doc->loadHTML($your_html);
foreach($doc->getElementsByTagName('iframe') as $iframe)
{
$iframe->setAttribute("src",$iframe->getAttribute('src').'?wmode=transparent');
}
echo $doc->saveHTML();