strncmp

(PHP 4, PHP 5)

strncmp — Binárně bezpečné porovnání prvních n znaků v řetězcích

Popis

int strncmp ( string $str1, string $str2, int $len )

This function is similar to strcmp(), with the difference that you can specify the (upper limit of the) number of characters (len) from each string to be used in the comparison. If any of the strings is shorter than len, then the length of that string will be used for the comparison.

Vrací < 0 pokud je str1 menší než str2; > 0 pokud je str1 větší než str2, a 0 pokud jsou shodné.

Pozn.: toto srovnání je case-sensitive.

Viz také: ereg(), strncasecmp(), strcasecmp(), substr(), stristr(), strcmp() a strstr().

add a note User Contributed Notes
strncmp

codeguru at crazyprogrammer dot cba dot pl
24-Jan-2008 08:07


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 01:46


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".

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strpbrk

strncasecmp

Last updated: Sat, 24 Mar 2007