php - Replace all matches within the tag

Answer

Solution:

(*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)
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Sample PHP Code:

$replaced = preg_replace('~<[^>]*>(*SKIP)(*F)|(hello)~i',
                        '<span class="page_speed_748935785">$1</span>',
                         $yourstring);
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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 captureshello (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

• How to match (or replace) a pattern except in situations s1, s2, s3...
• Article about matching a pattern unless...

Answer

Solution:

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";
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