strrpos
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().
strspn
(PHP 4, PHP 5)
strspn — Encuentra la longitud del primer segmento de un string que consista únicamente en caracteres contenidos dentro de una máscara dada.
Descripción
int strspn
( string $subject
, string $mask
[, int $start
[, int $length
]] )
Devuelve la longitud del primer grupo de caracteres consecutivos de mask encontrados en subject.
Si start y length son omitidos, entonces la totalidad de subject será examinada. Si son incluidos, entonces el efecto será el mismo que llamando strspn(substr($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");
?>
Parámetros
- subject
-
El string a examinar.
- mask
-
La lista de caracteres permitidos para incluir en los segmentos contados.
- 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 length es dado y no es negativo, entonces subject será examinado por el número length de caracteres después de la posición de inicio.
Si length es dado 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 str1 el cual enteramente consiste en caracteres en str2.
Historial de cambios
| Versión | Descripción |
|---|---|
| 4.3.0 | Fueron agregados los parámetros start y length |
Ejemplos
Example #1 Ejemplo de strspn()
<?php
echo strspn("foo", "o", 1, 2); // muestra: 2
?>
Notas
Note: Esta función es segura binariamente.
add a note
User Contributed Notes
strspn
mrsohailkhan at gmail dot com
01-Feb-2011 08:56
AT-HE (at_he.hotmail)
28-Nov-2010 10:45
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";
?>
Dmitry Mazur
04-Mar-2009 06:23
The second parameter is a set of allowed characters.
strspn will return an zero-based index of a first non-allowed character.
barry dot balkowski at gmail dot com
08-Aug-2008 09:12
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
B Crawford
03-Oct-2007 12:20
This function is significantly faster for checking illegal characters than the equivalent preg_match() method.