International PHP 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 $subject , string $mask [, int $start [, int $length ]] )

subject において mask 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。

If start and length are omitted, then all of subject will be examined. If they are included, then the effect will be the same as calling strcspn(substr($subject, $start, $length), $mask) (see substr for more information).

パラメータ

subject

調べたい文字列。

mask

許可しない文字をすべて含む文字列。

start

subject の中で調べ始める位置。

If start is given and is non-negative, then strcspn() will begin examining subject at the start'th position. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.

If start is given and is negative, then strspn() will begin examining subject at the start'th position from the end of subject.

length

subject の中での調べるセグメントの長さ。

If length is given and is non-negative, then subject will be examined for length characters after the starting position.

If length is given and is negative, then subject will be examined from the starting position up to length characters from the end of subject.

返り値

Returns the length of the initial segment of subject which consists entirely of characters not in mask.

注意:

When a start parameter is set, the returned length is counted starting from this position, not from the beginning of subject.

例1 strcspn() の例

<?php
$a 
strcspn('abcd',  'apple');
$b strcspn('abcd',  'banana');
$c strcspn('hello''l');
$d strcspn('hello''world');
$e strcspn('abcdhelloabcd''abcd', -9);
$f strcspn('abcdhelloabcd''abcd', -9, -5);

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

上の例の出力は以下となります。

int(0)
int(0)
int(2)
int(2)
int(5)
int(4)

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
2
legacyprog at routinz dot net
4 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
2
maskedcoder at hotmail dot com
9 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
Anonymous
5 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');
?>
up
1
AT-HE (at_he AT hotmai1 DOT com)
9 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";
}
?>
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