strncasecmp
For checking matches at the beginning of a short string, strpos() is about 15% faster than strncmp().
Here's a benchmark program to prove it:
<?php
$haystack = "abcdefghijklmnopqrstuvwxyz";
$needles = array('abc', 'xyz', '123');
foreach ($needles as $needle) {
$times['strncmp'][$needle] = -microtime(true);
for ($i = 0; $i < 1000000; $i++) {
$result = strncmp($haystack, $needle, 3) === 0;
}
$times['strncmp'][$needle] += microtime(true);
}
foreach ($needles as $needle) {
$times['strpos'][$needle] = -microtime(true);
for ($i = 0; $i < 1000000; $i++) {
$result = strpos($haystack, $needle) === 0;
}
$times['strpos'][$needle] += microtime(true);
}
var_export($times);
?>
strncmp
(PHP 4, PHP 5)
strncmp — Comparación segura a nivel binario de los primeros n caracteres entre strings
Descripción
int strncmp
( string $str1
, string $str2
, int $len
)
Esta función es similar a strcmp(), con la diferencia de que se puede especificar el (limite superior del) número de caracteres desde cada string a ser usado en la comparación.
Nótese que esta comparación es sensible a mayúsculas y minúsculas.
Parámetros
- str1
-
El primer string.
- str2
-
El segundo string.
- len
-
El número de caracteres para usar en la comparación.
Valores devueltos
Devueleve < 0 si str1 es menor que str2; > 0 si str1 es mayor que str2 y 0 si son iguales.
Ver también
- preg_match() - Realiza una comparación con una expresión regular
- strcmp() - Comparación de string segura a nivel binario
- strcasecmp() - Comparación de string segura a nivel binario e insensible a mayúsculas y minúsculas
- substr() - Devuelve parte de una cadena
- stristr() - strstr insensible a mayúsculas y minúsculas
- strncasecmp() - Comparación de los primeros n caracteres de cadenas, segura con material binario e insensible a mayúsculas y minúsculas
- strstr() - Buscar la primera aparición de una cadena
add a note
User Contributed Notes
strncmp
bobvin at pillars dot net
19-May-2011 02:25
elloromtz at gmail dot com
19-Apr-2010 12:25
if length is 0 regardless what the two strings are, it will return 0
<?php
strncmp("xybc","a3234",0); // 0
strncmp("blah123","hohoho", 0); //0
?>
codeguru at crazyprogrammer dot cba dot pl
24-Jan-2008 07:07
I ran the following experiment to compare arrays.
1 st - using (substr($key,0,5 == "HTTP_") & 2 nd - using (!strncmp($key, 'HTTP_', 5))
I wanted to work out the fastest way to get the first few characters from a array
BENCHMARK ITERATION RESULT IS:
if (substr($key,0,5 == "HTTP_").... - 0,000481s
if (!strncmp($key, 'HTTP_', 5)).... - 0,000405s
strncmp() is 20% faster than substr() :D
<?php
// SAMPLE FUNCTION
function strncmp_match($arr)
{
foreach ($arr as $key => $val)
{
//if (substr($key,0,5 == "HTTP_")
if (!strncmp($key, 'HTTP_', 5))
{
$out[$key] = $val;
}
}
return $out;
}
// EXAMPLE USE
?><pre><?php
print_r(strncmp_match($_SERVER));
?></pre>
will display code like this:
Array
(
[HTTP_ACCEPT] => XXX
[HTTP_ACCEPT_LANGUAGE] => pl
[HTTP_UA_CPU] => x64
[HTTP_ACCEPT_ENCODING] => gzip, deflate
[HTTP_USER_AGENT] => Mozilla/4.0
(compatible; MSIE 7.0;
Windows NT 5.1;
.NET CLR 1.1.4322;
.NET CLR 2.0.50727)
[HTTP_HOST] => XXX.XXX.XXX.XXX
[HTTP_CONNECTION] => Keep-Alive
[HTTP_COOKIE] => __utma=XX;__utmz=XX.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none)
)
Anonymous
17-Apr-2002 11:46
strncmp("sample","sam",4) returns 1 because the final requirement is if one string terminates before len, then the other must also terminate at that position.
You can imagine that all your strings have one more final, invisible "termination" character. If that termination character happens to be within in len, then it must match, too.
For instance, write that termination character with, say, the sequence "\0". Then you can equivalently consider that function call as strncmp("sample\0","sam\0",4).
So, the "p" in "sample" does not match the termination character in "sam".