(PHP 3>= 3.0.3, PHP 4 >= 4.0.0)
int strspn (string str1, string str2)
int strspn
Returns the length of the initial segment of str1 which consists entirely of characters in str2.
The line of code:
$var = strspn("42 is the answer, what is the question ...", "1234567890");
See also strcspn().