$re = '/^a*+b*+c*+d*+e*+f*+g*+h*+i*+j*+k*+l*+m*+n*+o*+p*+q*+r*+s*+t*+u*+v*+w*+x*+y*+z*+$/m';
$str = 'billowya';
preg_match_all($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