how to get:
WA4nNDfQ0wA
form this code:
<p>some text here ...</p>
<iframe width="640" height="360" src="//www.youtube.com/embed/WA4nNDfQ0wA?feature=player_embedded" frameborder="0" allowfullscreen></iframe>
<div>some text here ...</div>
<iframe width="640" height="360" src="//www.youtube.com/embed/9gypDWA6r2s?feature=player_embedded" frameborder="0" allowfullscreen></iframe>
by using php?
Assuming your html is inside the $html variable.
preg_match("|.*?/embed/([\w-]+)|", $html, $m);
print $m[1];
If you change the .*? into .*(greedy) then it will match the last id.