Matching an HTML (or XML) tag with a certain attribute value (e.g. class or tag) by Mike Malone (https://twitter.com/mjmalone)

gistfile1.php

function get_tag( $attr, $value, $xml, $tag=null ) {
  if( is_null($tag) )
    $tag = '\\w+';
  else
    $tag = preg_quote($tag);

  $attr = preg_quote($attr);
  $value = preg_quote($value);

  $tag_regex = "/<(".$tag.")[^>]*$attr\\s*=\\s*".
                "(['\\"])$value\\\\2[^>]*>(.*?)<\\/\\\\1>/"

  preg_match_all($tag_regex,
                 $xml,
                 $matches,
                 PREG_PATTERN_ORDER);

  return $matches[3];
}

// {<tag[^>]*attribute\\s*=\\s*(["'])value\\\\1[^>]*>(.*?)</tag>}