php preg_match_all：按第一个字符拆分字符串

I'd like to use PHP's preg_match_all function to split a string by a certain caracter, while the 'certain character' is the first character in the string, e.g.:

$pattern = '/#(?P<word>[.....])';
$string = 'one#two#three';
$matches = array();
preg_match_all($pattern,$string, $matches);
// expected $matches array: $matches['word'] = 'one','two','three'

So the "split field character" is itself part of the pattern (the first char).

Is this even possible? if yes, how?

Why you don't use explode?

$matches = explode('#', $string);