strcspn

(PHP 4, PHP 5)

strcspn — 获取不匹配遮罩的起始子字符串的长度

说明

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

返回 str1 中，所有字符都不存在于 str2 范围的起始子字符串的长度。

参数

str1: 第一个字符串。
str2: 第二个字符串。
start: 查找的起始位置。
length: 查找的长度。

返回值

以整型数返回子串的长度。

更新日志

版本	说明
4.3.0	新增 `start` 和 `length` 参数。

范例

Example #1 strcspn() example


<?php
$a = strcspn('abcd',  'apple');
$b = strcspn('abcd',  'banana');
$c = strcspn('hello', 'l');
$d = strcspn('hello', 'world');

var_dump($a);
var_dump($b);
var_dump($c);
var_dump($d);
?>

以上例程会输出：

int(0)
int(0)
int(2)
int(2)

注释

Note: 此函数可安全用于二进制对象。

参见

strspn() - 计算字符串中全部字符都存在于指定字符集合中的第一段子串的长度。

PHP手册 - N: 获取不匹配遮罩的起始子字符串的长度

用户评论:

legacyprog at routinz dot net (10-Dec-2010 03:20)

When you use the third parameter remember that the function will return the number of characters it bypassed, which will *not* be the position in your source string. It's a simple fix to just add your third parameter value to the function result to get the position in the first string where the scan stopped, but I didn't think of it at first.

Anonymous (16-Oct-2009 06:55)

strcspn() can also be thought of as analogous to the following regular expression: <?php // where ... represents the mask of characters preg_match('/[^ ...]/', substr($subject, $start, $length) ); ?> By this analogy, strcspn() can be used in place of some regular expressions to match a pattern without the overhead of a regex engine -- for example, ways to verify if an input string represents a binary value: <?php preg_match('/^[01]+$/i', $subject); // or... !preg_match('/[^01]/i', $subject); // ...or using strcspn() !strcspn($subject, '01'); ?>

Dmitry Mazur (04-Mar-2009 06:17)

The second parameter simply is the set of the "stop"-characters. In other words, this function will return the index (starting from 0) of a first occurence of the stop-character.

PHP at NospamImmortalSoFar dot com (08-Oct-2006 02:31)

Also useful for breaking down expressions - for example parsing SQL: values ('this', fn("that,)()", 4)) $sep = strcspn ($list, "'\"`"); // Start of quoted string $list = substr ($list, $sep); $find = substr ($list, 0, 1); while (($sep = strpos ($list, $find, $sep+1)) > 0 && substr ($list, $sep-1, 1) == '\\') {} // $sep now spans the entire string, regardless of embedded quotes Once the strings have been removed, an expression can then be parsed for commas and brackets without worrying about them: while ($out != '') { $sep = strcspn ($list, "(),"); // Next seperator ... }

AT-HE (at_he AT hotmai1 DOT com) (27-Dec-2005 10:07)

this function can be used like strspn(), except while that can be used to compare a string with an allowed pattern, this one can be use to compare a string with a FORBIDDEN pattern so, to know if any forbidden character has a position inside our string, we can use (not tested with backslashes)... <?php // LARGE VERSION $forbidden="\"\\?*:/@|<>"; if (strlen($filename) != strcspn($filename,$forbidden)) { echo "you cant create a file with that name!"; } // SHORT VERSION if (strlen($filename) - strcspn($filename,"\"\\?*:/@|<>")) { echo "i told you, you cant create that file"; } ?>

maskedcoder at hotmail dot com (11-Oct-2005 12:13)

useful for finding beginning of quotes and/or tags in a variable containing html. $pos = strcspn($data, '<"\''); will find the first occurance of either the beginning of a tag, or a double- or single-quoted string.