Returns the length of the initial segment of str1 which does not contain any of the characters in str2.
As of PHP 4.3.0, strcspn() accepts two optional integer parameters that can be used to define the start position and the length of the string to examine.
Megjegyzés: Ez a függvény "binary-safe", azaz helyesen kezeli a 127-es ASCII kód feletti karaktereket is.
See also strspn().