PHP - How to select random tag in the string

Question

For example, I have this string containing some number of iframe tags (but there can be also some text or links, so the point is to select only iframe tags):

<p><iframe frameborder="0" height="180" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaphchapeau-rouge-2022014%2F&amp;embed_type=widget_standard&amp;embed_uuid=9ff7c333-5c68-40d6-b9c7-b475c6a8d297&amp;hide_tracklist=1&amp;replace=0&amp;hide_cover=1"  width="600" ></iframe></p>

<p><iframe frameborder="0" height="180" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fx-tract-podcast-night-30-skaph%2F&amp;embed_type=widget_standard&amp;embed_uuid=7186f43a-4bc7-431d-8041-f51366355c44&amp;hide_tracklist=1&amp;replace=0&amp;hide_cover=1"  width="600" ></iframe></p>

<p><iframe frameborder="0" height="180" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaphclick-clack-07122013-experiment-liberec%2F&amp;embed_type=widget_standard&amp;embed_uuid=7f2202e6-fd70-45ac-ac1e-6c9dca0ad725&amp;hide_tracklist=1&amp;replace=0&amp;hide_cover=1"  width="600" ></iframe></p>

<p><iframe frameborder="0" height="180" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2FTFSpodcast%2Ftechno-for-soul-podcast-11-mixed-by-skaph%2F&amp;embed_type=widget_standard&amp;embed_uuid=e3f68ffd-488d-4d78-b369-a46c785f59a5&amp;hide_tracklist=1&amp;replace=0&amp;hide_cover=1"  width="600" ></iframe></p>

<p><iframe frameborder="0" height="180" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaphtechno-je-v%C5%A1echno-5%2F&amp;embed_type=widget_standard&amp;embed_uuid=2c80035e-27e8-4321-b07d-395e6777b98c&amp;hide_tracklist=1&amp;replace=0&amp;hide_cover=1"  width="600" ></iframe></p>

<p><iframe frameborder="0" height="132" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaphtechno-je-v%25C5%25A1echno-vol-2-liberec-experiment-18052013%2F&amp;embed_uuid=f81d24a4-c2f8-4bc5-a10f-7f3fb2243392&amp;stylecolor=&amp;embed_type=widget_standard" width="480"></iframe></p>

<p><iframe frameborder="0" height="132" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaphexperiment-18012013%2F&amp;embed_uuid=e63685e9-901c-4d71-a1c5-69d0afb130d6&amp;stylecolor=&amp;embed_type=widget_standard" width="480"></iframe></p>

<p><iframe frameborder="0" height="132" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaph-renaissance-winter-mix-2012%2F&amp;embed_uuid=5a7e4685-cf6a-4f84-ba1c-13251d5b7f59&amp;stylecolor=&amp;embed_type=widget_standard" width="480"></iframe></p>

<p><iframe frameborder="0" height="132" src="http://www.mixcloud.com/widget/iframe/?feed=http%3A%2F%2Fwww.mixcloud.com%2Fskaph%2Fskaph-mini-technik%2F&amp;embed_uuid=7818bedc-94d0-46b1-8193-4cafcf65ffb5&amp;stylecolor=&amp;embed_type=widget_standard" width="480"></iframe></p>

I need to select random iframe tag string from this and I need both opening and closing tag to be included. I suppose I should use something like explode and then use array_rand() function, but there is no divider. Other option that came to my mind is regex, but understanding of that still escapes me.

Answer 1

Regular expressions are not suitable for parsing HTML. Use a DOM parser instead -- here's a solution using PHP's native DOMDocument class:

$dom = new DOMDocument;
$dom->loadHTML($html);
$iframes = $dom->getElementsByTagName('iframe');

$index = mt_rand(0, $iframes->length);

$random_tag = $iframes->item($index);

In the above code, first a random index between 0 and the total number of tags ( $iframes->length ) is chosen with mt_rand() , and then the item() method is used to specifically access that tag. Once you have the tag, you can do any further processing. In the demo, I've shown you how to extract the src attribute just to show it's random.

Online demo