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 — Comparação de string segura para binário para os primeiros n caracteres
Descrição
int strncmp
( string $str1
, string $str2
, int $len
)
Esta função é similar a strcmp(), com a diferença que você pode especificar o limite superior de caracteres (len) de cada string para ser usado na comparação. Se qualquer uma das strings é menor do que len, então o tamanho desta string será usado para comparação.
Retorna < 0 se str1 é menor do que str2; > 0 se str1 é maior do que str2, e 0 se forem iguais.
Note que esta função diferencia maiúsculas e minúsculas.
Veja também ereg(), strncasecmp(), strcasecmp(), substr(), stristr(), strcmp(), e strstr().
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User Contributed Notes
strncmp
bobvin at pillars dot net
19-May-2011 07:25
elloromtz at gmail dot com
19-Apr-2010 05:25
if length is 0 regardless what the two strings are, it will return 0
<?php
strncmp("xybc","a3234",0); // 0
strncmp("blah123","hohoho", 0); //0
?>
codeguru at crazyprogrammer dot cba dot pl
24-Jan-2008 11:07
I ran the following experiment to compare arrays.
1 st - using (substr($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 04:46
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".