strrpos
Re:Dmitry Mazur
[quote]strspn will return an zero-based index of a first non-allowed character.[/quote]
That's incorrect. As noted above in the documentation and below in barry's note, strspn returns the length of the longest substring in $str1 consisting exclusively of characters from $str2.
If strspn returned the index of the first non-allowed character, then Example #1 in the documentation should not return 2, since it starts searching from the first _allowed_ character. Had the $start and $length parameters been omitted, the code would still return 2 (not 0, as it would be if you were correct), since the length of the longest substring of "foo" containing only the letter "o" is 2.
strspn
(PHP 4, PHP 5)
strspn — Find length of initial segment matching mask
说明
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");
?>
参数
- 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.
返回值
Returns the length of the initial segment of str1 which consists entirely of characters in str2 .
更新日志
| 版本 | 说明 |
|---|---|
| 4.3.0 | The start and length parameters were added |
范例
Example#1 strspn() example
<?php
echo strspn("foo", "o", 1, 2); // 2
?>
注释
Note: 本函数可安全用于二进制对象。
add a note
User Contributed Notesstrspn
XZero
01-Jul-2009 10:23
01-Jul-2009 10:23
Dmitry Mazur
05-Mar-2009 02:23
05-Mar-2009 02:23
The second parameter is a set of allowed characters.
strspn will return an zero-based index of a first non-allowed character.
barry dot balkowski at gmail dot com
08-Aug-2008 05:12
08-Aug-2008 05:12
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 08:20
03-Oct-2007 08:20
This function is significantly faster for checking illegal characters than the equivalent preg_match() method.