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.
(PHP 4, PHP 5, PHP 7, PHP 8)
strcspn — Find length of initial segment not matching mask
Returns the length of the initial segment of
string which does not
contain any of the characters in characters.
If offset and length
are omitted, then all of string will be
examined. If they are included, then the effect will be the same as
calling strcspn(substr($string, $offset, $length),
$characters) (see substr
for more information).
stringThe string to examine.
charactersThe string containing every disallowed character.
offset
The position in string to
start searching.
If offset is given and is non-negative,
then strcspn() will begin
examining string at
the offset'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 offset is given and is negative,
then strcspn() will begin
examining string at
the offset'th position from the end
of string.
length
The length of the segment from string
to examine.
If length is given and is non-negative,
then string will be examined
for length characters after the starting
position.
If length is given and is negative,
then string will be examined from the
starting position up to length
characters from the end of string.
Returns the length of the initial segment of string
which consists entirely of characters not in characters.
Зауваження:
When a
offsetparameter is set, the returned length is counted starting from this position, not from the beginning ofstring.
| Версія | Опис |
|---|---|
| 8.4.0 |
Prior to PHP 8.4.0, when characters was the empty string,
the search would incorrectly stop at the first null byte in string.
|
| 8.0.0 |
length is nullable now.
|
Приклад #1 strcspn() example
<?php
$a = strcspn('banana', 'a');
$b = strcspn('banana', 'abcd');
$c = strcspn('banana', 'z');
$d = strcspn('abcdhelloabcd', 'a', -9);
$e = strcspn('abcdhelloabcd', 'a', -9, -5);
var_dump($a);
var_dump($b);
var_dump($c);
var_dump($d);
var_dump($e);
?>Поданий вище приклад виведе:
int(1) int(0) int(6) int(5) int(4)
Зауваження: Ця функція є бінарно безпечною.
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.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";
}
?>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.It might not be clear from the example, that
strcspn('abcdhelloabcd', 'abcd', -9, -5) == 4
because it's only evaluating 'hell' which doesn't contain any mask, so returns strlen('hell').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');
?>