Online PHP editor | output for R1aql

<?php function validateHtml($html) { $stack = array(); $tags = preg_split("/(<[^>]+>)/", $html, -1, PREG_SPLIT_DELIM_CAPTURE); foreach ($tags as $tag) { if (preg_match("/^<\/\s*([^\s>]+)\s*>$/", $tag, $matches)) { // closing tag $last = array_pop($stack); if (!$last || $last !== $matches[1]) { return false; } } elseif (preg_match("/^<\s*([^\s>]+)(\s+[^>]+)?\s*>$/", $tag, $matches)) { // opening tag array_push($stack, $matches[1]); } } return count($stack) === 0; } // example usage $html = "<div><p>Some text</p></div>"; var_dump(validateHtml($html)); // true $html = "<div><p>Some text</div>"; var_dump(validateHtml($html)); // false $html = "<div><p>Some text</p><span></span></div>"; var_dump(validateHtml($html)); // true $html = "<div><p>Some text<span></p></span></div>"; var_dump(validateHtml($html)); // false