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Editorial Team
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Asked: 2026-05-15T00:53:21+00:00

Consider the following situation: I want to replace links in a string, specifically I

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Consider the following situation: I want to replace links in a string, specifically I want to add a “search engine” link next to it.

Think: Link Title (S), where as S will link to Google with “Link Title” as search term. I’ve copied a real life example string ($content) in the code so you can reproduce this 1:1 in PHP code.

// PCRE case-insensitive, all as a single string, ungreedy and evaluate PHP replace.
$content = '<h3 class="bgg2" style="padding: 4px 0px 4px 5px; font-size: 11px;">» <a href="/forum_detail.html?topic=3456&amp;start=20&amp;post=97145#p97145" class="nub" title="Xenoblade: Japanischer TV-Spot"><b>Xenoblade: Japanischer TV-Spot</b></a></h3>';

$replace = preg_replace('/(<a.*>)(.*)<\/a>/isUe', ('"\1\2</a>&nbsp;(<a href=\"http://www.google.com/search?q=' . strip_tags(strtoupper('blah\2')) . '\">S</a>)"'), $content);

print($replace);

Output (incorrect):
Xenoblade: Japanischer TV-Spot (S) -> when you look at the HTML it looks like this:

<a href="http://www.google.com/search?q=BLAH%3Cb%3EXenoblade:%20Japanischer%20TV-Spot%3C/b%3E">S</a>

The strtoupper() did get the literal string blah -> BLAH but not the \2 back reference from the regular expression?

It looks like the \2 back referenced string is used BEFORE strtoupper() or strip_tags() functions are executed – some kind of timing of evaluation versus functions in PHP perhaps?

Does anybody know how to explain this bevhaviour?

—

I’ve developed a workaround using preg_replace_callback, still I’m puzzled about why the above code doesn’t work as I expected.

For reference to see what I want to achive:

Solution

// I have to use PHP < 5.0 so create_function() will do the job.
$replace = preg_replace_callback('/(<a.*>)(.*)<\/a>/isU',
create_function('$matches', 'return $matches[1] . $matches[2] . \'</a>&nbsp;(<a href="http://www.google.com/search?q=\' . strip_tags(strtoupper($matches[2])) . \'">S</a>)\';'),
$content);

print($replace);

Output (correct):
Xenoblade: Japanischer TV-Spot (S) -> when you look at the HTML it looks like this:

<a href="http://www.google.com/search?q=XENOBLADE:%20JAPANISCHER%20TV-SPOT">S</a>

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1 Answer

  1. Editorial Team

    Change

    '"\1\2</a>&nbsp;(<a href=\"http://www.google.com/search?q=' . strip_tags(strtoupper('blah\2')) . '\">S</a>)"'

    to

    '"\1\2</a>&nbsp;(<a href=\"http://www.google.com/search?q=" . strip_tags(strtoupper(\'blah\2\')) . "\">S</a>)"'

    The strip_tags() function needs to be a part of the replacement string so it doesn’t get evaluated before it gets passed to preg_replace().

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