strspn
(PHP 4, PHP 5)
strspn — Возвращает длину участка в начале строки, полностью соответствующего маске
Описание
$subject
, string $mask
[, int $start
[, int $length
]] )
Возвращает длину участка от начала строки subject,
содержащий только символы из mask.
Если параметры start и length
не указаны, то будет исследована вся строка subject.
Если они указаны, то эффект будет аналогичен вызову
strspn(substr($subject, $start, $length) $mask)
(подробнее см. функцию substr).
Строка кода:
<?php
$var = strspn("42 is the answer to the 128th question.", "1234567890");
?>
subject,
состоящий только из символов "1234567890".
Список параметров
-
subject -
Исследуемая строка.
-
mask -
Список из разрешенных символов.
-
start -
Позиция начала поиска в
subject.Если
startуказан и неотрицателен, то strspn() начнет искать в строкеsubjectначиная с позицииstart. К примеру, в строке 'abcdef', символом с позицией 0 является 'a', символом с позицией 2 является 'c' и т.д.Если
startуказан и отрицателен, то strspn() начнет поиск в строкеsubjectс позиции, отстоящей наstartсимволов с концаsubject. -
length -
Длина исследуемого фрагмента
subject.Если
lengthуказан и неотрицателен, то строкаsubjectбудет исследована в течениеlengthпосле стартовой позиции.Если
lengthуказана и отрицательна, то строкаsubjectбудет исследована начиная со стартовой позиции до позиции, отстоящей наlengthсимволов с концаsubject.
Возвращаемые значения
Возвращает длину первого участка subject,
состоящего целиком из символов в mask.
Список изменений
| Версия | Описание |
|---|---|
| 4.3.0 |
Добавлены параметры start и length
|
Примеры
Пример #1 Пример использования strspn()
<?php
// subject не начинается ни из какого символа из mask
var_dump(strspn("foo", "o"));
// проверить два символа из subject начиная с позиции 1
var_dump(strspn("foo", "o", 1, 2));
// проверить один символ из subject начиная с позиции 1
var_dump(strspn("foo", "o", 1, 1));
?>
Результат выполнения данного примера:
int(0) int(2) int(1)
Примечания
Замечание: Эта функция безопасна для обработки данных в двоичной форме.
- addcslashes
- addslashes
- bin2hex
- chop
- chr
- chunk_split
- convert_cyr_string
- convert_uudecode
- convert_uuencode
- count_chars
- crc32
- crypt
- echo
- explode
- fprintf
- get_html_translation_table
- hebrev
- hebrevc
- hex2bin
- html_entity_decode
- htmlentities
- htmlspecialchars_decode
- htmlspecialchars
- implode
- join
- lcfirst
- levenshtein
- localeconv
- ltrim
- md5_file
- md5
- metaphone
- money_format
- nl_langinfo
- nl2br
- number_format
- ord
- parse_str
- printf
- quoted_printable_decode
- quoted_printable_encode
- quotemeta
- rtrim
- setlocale
- sha1_file
- sha1
- similar_text
- soundex
- sprintf
- sscanf
- str_getcsv
- str_ireplace
- str_pad
- str_repeat
- str_replace
- str_rot13
- str_shuffle
- str_split
- str_word_count
- strcasecmp
- strchr
- strcmp
- strcoll
- strcspn
- strip_tags
- stripcslashes
- stripos
- stripslashes
- stristr
- strlen
- strnatcasecmp
- strnatcmp
- strncasecmp
- strncmp
- strpbrk
- strpos
- strrchr
- strrev
- strripos
- strrpos
- strspn
- strstr
- strtok
- strtolower
- strtoupper
- strtr
- substr_compare
- substr_count
- substr_replace
- substr
- trim
- ucfirst
- ucwords
- vfprintf
- vprintf
- vsprintf
- wordwrap
Коментарии
This function is significantly faster for checking illegal characters than the equivalent preg_match() method.It took me some time to understand the way this function works…
I’ve compiled my own explanation with my own words that is more understandable for me personally than the official one or those that can be found in different tutorials on the web.
Perhaps, it will save someone several minutes…
<?php
strspn(string $haystack, string $char_list [, int $start [, int $length]])
?>
The way it works:
- searches for a segment of $haystack that consists entirely from supplied through the second argument chars
- $haystack must start from one of the chars supplied through $char_list, otherwise the function will find nothing
- as soon as the function encounters a char that was not mentioned in $chars it understands that the segment is over and stops (it doesn’t search for the second, third and so on segments)
- finally, it measures the segment’s length and return it (i.e. length)
In other words it finds a span (only the first one) in the string that consists entirely form chars supplied in $chars_list and returns its length
The second parameter is a set of allowed characters.strspn will return an zero-based index of a first non-allowed character.
you can use this function with strlen to check illegal characters, string lenght must be the same than strspn (characters from my string contained in another)
<?php
$digits='0123456789';
if (strlen($phone) != strspn($phone,$digits))
echo "illegal characters";
?>
very dificult to get from the definition directly, while i search for that,i came to know that
strspn() will tell you the length of a string consisting entirely of the set of characters in accept set. That is, it starts walking down str until it finds a character that is not in the set (that is, a character that is not to be accepted), and returns the length of the string so far.
and
strcspn() works much the same way, except that it walks down str until it finds a character in the reject set (that is, a character that is to be rejected.) It then returns the length of the string so far.
<?php
$acceptSet = "aeiou";
$rejectSet = "y";
$str1 ="a banana";
$str2 ="the bolivian navy on manuvers in the south pacific";
echo $n = strspn($str1,$acceptSet);// $n == 1, just "a"
echo $n = strcspn($str2,$rejectSet);// n = 16, "the bolivian nav"
?>
hope this example will help in understanding the concept of strspn() and strcspn().
Quick way to check if a string consists entirely of characters within the mask is to compare strspn with strlen eg:
<?php
$path = $_SERVER['PATH_INFO'];
if (strspn($path,'/') == strlen($path)) {
//PATH_INFO is empty
}
?>
strspon and preg_match seem to be equally fast for validating numbers:
<?php
$testValInvalid = 'foobar123^^';
$testValValid = '12346';
$allowedChars = '1234567890';
$t1 = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
assert(strspn($testValInvalid, $allowedChars) != strlen($testValInvalid));
assert(strspn($testValValid, $allowedChars) == strlen($testValValid));
}
print 'Time taken for strspon: ' . (microtime(true) - $t1);
print PHP_EOL;
$t1 = microtime(true);
for ($i = 0; $i < 1000000; $i++) {
assert(preg_match('/^[0-9]+$/', $testValInvalid) === 0);
assert(preg_match('/^[0-9]+$/', $testValValid));
}
print 'Time taken for preg_match: ' . (microtime(true) - $t1);
print PHP_EOL;
/**
nino-mcb:hosp_web ninoskopac$ php test.php
Time taken for strspon: 3.24165391922
Time taken for preg_match: 3.1820080280304
nino-mcb:hosp_web ninoskopac$ php test.php
Time taken for strspon: 3.1806418895721
Time taken for preg_match: 3.2244551181793
*/
?>
Get Group match letter
<?php
$s= 'aaabbbcceeffaaeeeaaabbzmmm';
function groupby( $s ){
static $a = [];
static $i = 0;
$o = strspn( $s, $s[$i], $i);
$a[ $i ] = [ $s[$i] => $o ];
$i += $o;
if( $i < strlen($s) ) {
groupby($s);
}
return $a;
}
print_r(groupby($s));
?>