strspn

(PHP 4, PHP 5)

strspn — Find length of initial segment matching mask

Description

int strspn ( string $str1 , string $str2 [, int $start [, int $length ]] )

Finds the length of the initial segment matching mask.

The line of code:


<?php
$var = strspn("42 is the answer, what is the question ...", "1234567890");
?>

will assign 2 to $var, because the string "42" will be the longest segment containing characters from "1234567890".

Parameters

str1: The first string.
str2: The second string.
start: The start position of the string to examine. Negative value counts position from the end of a string.
length: The length of the string to examine. Negative value sets length from the end of a string.

Return Values

Returns the length of the initial segment of str1 which consists entirely of characters in str2 .

ChangeLog

Version	Description
4.3.0	The `start` and `length` parameters were added

Examples

Example #1 strspn() example


<?php
echo strspn("foo", "o", 1, 2); // 2
?>

Notes

Note: This function is binary-safe.


It took me some time to understand the way this function works…

I’ve compiled my own explanation with my own words that is more understandable for me personally than the official one or those that can be found in different tutorials on the web.

Perhaps, it will save someone several minutes…



<?php 

strspn(string $haystack, string $char_list [, int $start [, int $length]])

?>



The way it works:

 -   searches for a segment of $haystack that consists entirely from supplied through the second argument chars 

 -   $haystack must start from one of the chars supplied through $char_list, otherwise the function will find nothing

 -   as soon as the function encounters a char that was not mentioned in $chars it understands that the segment is over and stops (it doesn’t search for the second, third and so on segments)

 -   finally, it measures the segment’s length and return it (i.e. length)



In other words it finds a span (only the first one) in the string that consists entirely form chars supplied in $chars_list and returns its length

B Crawford
03-Oct-2007 02:20


This function is significantly faster for checking illegal characters than the equivalent preg_match() method.

add a note

strstr

strrpos

Last updated: Fri, 10 Oct 2008