Returns the length of the initial segment of str1 which consists entirely of characters in str2.
The line of code:
will assign 2 to $var, because the string "42" will be the longest segment containing characters from "1234567890".As of PHP 4.3.0, strspn() accepts two optional integer parameters that can be used to define the start position and the length of the string to examine.
注: 该函数可安全用于二进制对象。
See also strcspn().