How to Extract the URL from A String in PHP?

Question

I'm using PHP's "simplexml_load_file" to get some data from Flickr.

My goal is to get the photo url.

I'm able to get the following value (assigned to PHP variable):

<p><a href="http://www.flickr.com/people/19725893@N00/"&gt;codewrecker&lt;/a&gt; posted a photo:</p>

<p><a href="http://www.flickr.com/photos/19725893@N00/2302759205/" title="Santa Monica Pier"><img src="http://farm3.static.flickr.com/2298/2302759205_4fb109f367_m.jpg" width="180" height="240" alt="Santa Monica Pier" /></a></p>

How can I extract just this part of it?

http://farm3.static.flickr.com/2298/2302759205_4fb109f367_m.jpg

Just in case it helps, here's the code I'm working with:

<?php
$xml = simplexml_load_file("http://api.flickr.com/services/feeds/photos_public.gne?id=19725893@N00&amp;lang=en-us&amp;format=xml&amp;tags=carousel");
foreach($xml->entry as $child) {
    $flickr_content = $child->content; // gets html including img url
    // how can I get the img url from "$flickr_content"???
 }
?>

Answer 1

You can probably get away with using a regular expression for this, assuming that the way the HTML is formed is pretty much going to stay the same, e.g.:

if (preg_match('/<img src="([^"]+)"/i', $string, $matches)) {
    $imageUrl = $matches[1];   
}

This is fairly un-robust, and if the HTML is going to change (e.g. the order of parameters in the <img> tag, risk of malformed HTML etc.), you would be better off using an HTML parser.

Answer 2

Easy way: Combination of substr and strpos to extract first the tag and then the src='...' value, and finally the target string.

Slightly more difficult way (BUT MUCH MORE ROBUST): Use an XML parsing library such as simpleXML

Answer 3

It's not solving your problem(and probably total overkill), but worth mentioning because I've used the library on 2 projects and it's well written.

phpFlickr - http://phpflickr.com/

Answer 4

I hope this is helpful. I enjoy using xpath to cut through the XML I get back from SimpleXML:

<?php
$xml = new SimpleXMLElement("http://api.flickr.com/services/feeds/photos_public.gne?id=19725893@N00&amp;lang=en-us&amp;format=xml&amp;tags=carousel", NULL, True);
$images = $xml->xpath('//img');  //use xpath on the XML to find the img tags

foreach($images as $image){  
    echo $image['src'] ;  //here is the image URL
}
?>