php regex to add class to images without class - php

Question

I'm looking for a php regex to check if a image don't have any class, then add "img-responsive" to that image's class.
thank you.

Answer 1

Instead of looking to implement a regular expression, make effective use of DOM instead.
$doc = new DOMDocument;
$doc->loadHTML($html); // load the HTML data
$imgs = $doc->getElementsByTagName('img');
foreach ($imgs as $img) {
if (!$img->hasAttribute('class'))
$img->setAttribute('class', 'img-responsive');
}

Answer 2

I would be tempted to do this in JQuery. That offers all the functionality you need in a few lines.
$(document).ready(function(){
$('img').not('img[class]').each(function(e){
$(this).addClass('img-responsive');
});
});

Answer 3

If you have the output in PHP then a HTML parser is the way to do it. Regular expressions will always fail, in the end. If you don't want to use a parser, but you have the HTML code you can try to do it with plain and simple PHP code:
function addClassToImagesWithout($html)
// this function does what you want, given well-formed html
{
// cut into parts where the images are
$parts = explode('<img',$html);
foreach ($parts as $key => $part)
{
// spilt at the end of tags, the image args are in the first bit
$bits = explode('>',$part);
// does it not contain a class
if (strpos($bits[0],'class=') !== FALSE)
{
// insert the class
$bits[0] .= " class='img-responsive'";
}
// recombine the bits
$part[$key] = implode('>',$bits);
}
// recombine the parts and return the html
return implode('<img',$parts);
}
this code is untested and far from perfect, but it shows that regular expressions are not needed. You will have to add in some code to catch exceptions.
I must stress that this code, just like regular expressions will ultimately fail when, for instance, you have something like id='classroom', title='we are a class apart' or similar. To do a better job you should use a parser:
http://htmlparsing.com/php.html