strspn

(PHP 4, PHP 5, PHP 7, PHP 8)

strspn — Averigua la longitud del segmento inicial de un string que consista únicamente en caracteres contenidos dentro de una máscara dada

Descripción

strspn(
    string $subject,
    string $mask,
    int $start = ?,
    int $length = ?
): int

Encuentra la longitud del segmento inicial de subject que contiene solamente caracteres de mask.

Si start y length son omitidos, entonces la totalidad de subject será examinada. Si son incluidos, entonces el efecto será el mismo que llamando strspn(substr($subject, $start, $length), $mask) (ver substr para más información).

La línea de código:

<?php
$var = strspn("42 is the answer to the 128th question.", "1234567890");
?>

asignará 2 a $var, debido a que el string "42" es el segmento inicial de subject que consiste solamente en caracteres contenidos dentro de "1234567890".

Parámetros

subject

El string a examinar.

mask

La lista de caracteres permitidos.

start

La posición en subject donde iniciar la búsqueda.

Si start es dado y no es negativo, entonces strspn() comenzará a examinar a subject en la posición startésima. Por ejemplo, en el string 'abcdef', el caracter en la posición 0 es 'a', el caracter en la posición 2 es 'c' y así sucesivamente.

Si start es dado y es negativo, entonces strspn() comenzará a examinar subject desde la startésima posición desde el final de subject.

length

La longitud del segmento de subject a examinar.

Si se proporciona length y no es negativo, entonces subject será examinado por el número length de caracteres después de la posición de inicio.

Si se proporciona length y es negativo, entonces subject sera examinado desde la posición de inicio hasta el número length de caracteres desde el final de subject.

Valores devueltos

Devuelve la longitud del segmento inicial de subject el cual enteramente consiste en caracteres en mask.

Nota:
Cuando se establece el parámetro start, la longitud devuelta se cuenta a partir de esta posición, no desde el comienzo de subject.

Ejemplos

Ejemplo #1 Ejemplo de strspn()

<?php
// subject no inicia con ningún caracter de mask
var_dump(strspn("foo", "o"));

// examina dos caracteres de subject iniciando en el offset 1
var_dump(strspn("foo", "o", 1, 2));

// examina un caracter de subject iniciando en el offset 1
var_dump(strspn("foo", "o", 1, 1));
?>

El resultado del ejemplo sería:

int(0)
int(2)
int(1)

Notas

Nota: Esta función es segura binariamente.

Ver también

strcspn() - Averiguar la longitud del segmento inicial que no coincida con una máscara

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User Contributed Notes 8 notes

down

barry dot balkowski at gmail dot com ¶

16 years ago

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

down

AT-HE (at_he.hotmail) ¶

14 years ago

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";

?>

down

B Crawford ¶

17 years ago

This function is significantly faster for checking illegal characters than the equivalent preg_match() method.

down

mrsohailkhan at gmail dot com ¶

13 years ago

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().

down

Dmitry Mazur ¶

15 years ago

The second parameter is a set of allowed characters.
strspn will return an zero-based index of a first non-allowed character.

down

bob at example dot com ¶

12 years ago

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

}

?>

down

lincoln dot mahmud at gmail dot com ¶

4 years ago

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));

?>

down

-1

nino dot skopac at gmail dot com ¶

6 years ago

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
 */
?>

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