PHP Australia Conference 2015

strcspn

(PHP 4, PHP 5)

strcspnマスクにマッチしない最初のセグメントの長さを返す

説明

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

str1 において str2 の文字がどれも含まれていない最初のセグメントの長さを返します。

パラメータ

str1

最初の文字列。

str2

2 番目の文字列。

start

調べ始める位置。

length

調べる文字列の長さ。

返り値

セグメントの長さを返します。

例1 strcspn() の例

<?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);
?>

上の例の出力は以下となります。

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

注意

注意: この関数はバイナリデータに対応しています。

参考

  • strspn() - 指定したマスク内に含まれる文字からなる文字列の最初のセグメントの長さを探す

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User Contributed Notes 4 notes

up
1
maskedcoder at hotmail dot com
8 years ago
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.
up
1
AT-HE (at_he AT hotmai1 DOT com)
8 years ago
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";
}
?>
up
0
legacyprog at routinz dot net
3 years ago
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.
up
-1
Anonymous
4 years ago
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');
?>
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