3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = <<<STR This is <a href="http://foo.com">This is #foo</a>. Simple #html-stuff text <a href="http://foobar.com#baz">#simple</a> <span class="simple">simple #simple text text</span> <span>foo #simple"onclick="alert('hi')" another STR; echo preg_replace('/(?!<a[^<>]*>[^#]+)#(\b[-_\w]+\b)(?![^<]*<\/a>)/', '<a href="/tags/$1">#$1</a>', $str);

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42.65 ms | 402 KiB | 5 Q