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strcspn — 获取不匹配遮罩的起始子字符串的长度
$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。
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。
以整型数返回子串的长度。
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 ( $d );
?>
以上例程会输出:
int(0) int(0) int(2) int(2)
Note: 此函数可安全用于二进制对象。
[#1] legacyprog at routinz dot net [2010-12-09 19:20:08]
When you use the third parameter remember that the function will return the number of characters it bypassed, which will *not* be the position in your source string. It's a simple fix to just add your third parameter value to the function result to get the position in the first string where the scan stopped, but I didn't think of it at first.
[#2] Anonymous [2009-10-16 10:55:56]
strcspn() can also be thought of as analogous to the following regular expression:
<?php
// where ... represents the mask of characters
preg_match('/[^ ...]/', substr($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');
?>
[#3] AT-HE (at_he AT hotmai1 DOT com) [2005-12-27 02:07:12]
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";
}
?>
[#4] maskedcoder at hotmail dot com [2005-10-10 16:13:50]
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.