PHP strspn() Function

The strspn() function is an in-built function in PHP which finds the length of the initial segment of a string consisting entirely of characters contained within a given list of characters passed as a parameter to the function.

Syntax :

strspn( $string, $charlist, $start, $length)

Parameters : This function accepts four parameters as shown in the above syntax. First two parameters are mandatory and must be supplied while the remaining two parameters are optional. All of these parameters are described below:

• $string : This mandatory parameter specifies the string to search.
• $charlist : This mandatory parameter specifies the list of characters to be searched in the given $string.
• $start : This optional parameter specifies the index from where we want to start searching in the string.
  • If $start is given and is non-negative, then strspn() will begin examining $string from that position.
  • If $start is given and is negative, then strspn() will begin examining $string from that position from the end of $string.
• $length : It specifies the number of characters of $string which are needed to be searched. Its default value is till the end of the $string.
  • If $length is given and is non-negative, then $string will be examined for $length characters from the starting position.
  • If $length is given and is negative, then $string will be examined from the starting position up to $length characters from the end of $string.

Return Value: This function returns the number of characters found in the string that contains only characters from the charlist parameter.

Examples:

Input : $string = "abcdefghijk", $charlist = "abcjkl"
Output : 3

Input : $string = "Geeks for Geeks", $charlist = "Geeksfor "
Output : 15

Below programs illustrate the strspn() function:

Program 1:

<?php
// Output is 15 because whole input string
// contains all characters from given char list
// "Geeksfor "
echo strspn("Geeks for Geeks", "Geeksfor ");
?>

Output:

15

Program 2: This program illustrates the case-sensitivity of strspn() function.

<?php
// Output is 0 because there is no substring
// which contains all characters of given char
// list.
echo strspn("Geeks for Geeks", "geeks");
?>

Output:

0

Program 3: This program illustrates the use of strspn() function with $start and $length parameters.

<?php
// Searches substring starting from index 5
// and length 9 with all characters in char
// list " for"
echo strspn("Geeks for Geeks", " for", 5, 9);
?>

Output:

5

Program 4: This program illustrates the use of strspn() function with negative $length parameter.

<?php
// Searches from index 5 till 5-th position from
// end.
echo strspn("Geeks for Geeks", " for", 5, -5);
?>

Output:

5

Program 5: This program illustrates the use of strspn() function with a negative $start parameter.

<?php
// Searches from 5-th index from end
echo strspn("Geeks for Geeks", "for", -5);
?>

Output:

0

Reference:
http://php.net/manual/en/function.strspn.php