$re = '~<\s*(?:/\s*)?(?:p|a|strong)\s*>~m';
$str = '<p > ¡Esto es una prueba! < /p > <p> <strong > Prueba 123 </strong> </p> <p> <strong> <a href="https://matricom.net"> MATRICOM < / a> </ strong> </p> <p> <strong > Todas las pruebas aquí ... </strong > < /p>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php