Replace all matches within the tag

Question

There is the following line:

$str = '<div class="hello"> Hello world &lt hello world?! </div>';

Need to find all the matches within the tag, while avoiding a match attribute values. Try something like:

$pattern = '/(.*)(hello)(.*)(?=<\/)/ui'; 
$replacement = '$1<span style="background:yellow">$2</span>$3';

but yet there is only one "hello". What to do?

So in your sample you would expect to find the two hellos inside the div, but not the .hello class? You might be better off using DomDocument (http://php.net/manual/en/class.domdocument.php) — jrjohnson, Jul 18 '14 at 05:46

score 2 · Answer 1 · edited May 23 '17 at 11:57

(*SKIP)(*F) Syntax in Perl and PCRE (PHP, Delphi, R...)

With all the disclaimers about using regex to parse html, we can do this with a surprisingly simple regex:

<[^>]*>(*SKIP)(*F)|(hello)

Sample PHP Code:

$replaced = preg_replace('~<[^>]*>(*SKIP)(*F)|(hello)~i',
                        '<span style="background:yellow">$1</span>',
                         $yourstring);

In the regex demo, see the substitutions at the bottom.

Explanation

This problem is a classic case of the technique explained in this question to "regex-match a pattern, excluding..."

The left side of the alternation | matches complete <tags> then deliberately fails, after which the engine skips to the next position in the string. The right side captures hello (case-insensitive to Group 1, and we know they are the right ones because they were not matched by the expression on the left.

Reference

FYI: Added demo and explanation. :) – zx81 Jul 18 '14 at 05:58 — zx81, Jul 18 '14 at 05:58

Ja͢ck · Answer 2 · 2014-07-18T06:38:29.573

Wrapping text matches into another element is a pretty basic operation, though the code is somewhat tricky:

$html = <<<EOS
<div class="hello"> Hello world &lt; hello world?! </div>
EOS;

$dom = new DOMDocument;
$dom->loadHTML($html);

$search = 'hello';

foreach ($dom->getElementsByTagName('div') as $element) {
    foreach ($element->childNodes as $node) { // iterate all direct descendants
        if ($node->nodeType == 3) { // and look for text nodes in particular
            if (($pos = strpos($node->nodeValue, $search)) !== false) {
                // we split the text up in: <prefix> match <postfix>
                $postfix = substr($node->nodeValue, $pos + strlen($search));
                $node->nodeValue = substr($node->nodeValue, 0, $pos);

                // insert <postfix> behind the current text node
                $textNode = $dom->createTextNode($postfix);
                if ($node->nextSibling) {
                    $node->parentNode->insertBefore($textNode, $node->nextSibling);
                } else {
                    $node->parentNode->appendChild($textNode);
                }

                // wrap match in an element and insert it    
                $wrapNode = $dom->createElement('span', $search);
                $element = $node->parentNode->insertBefore($wrapNode, $textNode);
            }
        }
    }
}

echo $dom->saveHTML(), "\n";

Replace all matches within the tag

2 Answers2