$re = '/^\S+\h\S+\K\h/m';
$str = '20 DE NOVIEMBRE
CENTRO
EL ARENAL 4A SECCION
IGNACIO ZARAGOZA
JARDIN BALBUENA
MOCTEZUMA 2A SECCION
MORELOS
PEON DE LOS BAOS';
$subst = "\n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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