Get tag contents from html

function.php

<?php

/**
 * @param string $tagName
 * @param string $content
 */
function getTagContents($tagName, $content)
{
	  preg_match_all(sprintf('#<%1$s[^>]+>(.*?)</%1$s>#ism', $tagName), $content, $match);
    return isset($match[1]) ? $match[1] : array();
}

$string='My <strong>dog</strong> is <strong>missing</strong>.';
print_r(getTagContents('strong', $string));