PHP: Best way to split string into alphabetic and numeric components

Question

I have several strings of the format

AA11
AAAAAA1111111
AA1111111

Which is the best (most efficient) way to sepa

Answer 1

If they're all a series of alpha, followed by a series of numeric, with no non-alphameric characters, then sscanf() is probably more efficient than regexp

$example = 'AAA11111';
list($alpha,$numeric) = sscanf($example, "%[A-Z]%d");

var_dump($alpha);
var_dump($numeric);