PHP Australia Conference 2015

strncmp

(PHP 4, PHP 5)

strncmpBinary safe string comparison of the first n characters

Description

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 from each string to be used in the comparison.

Note that this comparison is case sensitive.

Parameters

str1

The first string.

str2

The second string.

len

Number of characters to use in the comparison.

Return Values

Returns < 0 if str1 is less than str2; > 0 if str1 is greater than str2, and 0 if they are equal.

See Also

  • preg_match() - Perform a regular expression match
  • strcmp() - Binary safe string comparison
  • strcasecmp() - Binary safe case-insensitive string comparison
  • substr() - Return part of a string
  • stristr() - Case-insensitive strstr
  • strncasecmp() - Binary safe case-insensitive string comparison of the first n characters
  • strstr() - Find first occurrence of a string

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User Contributed Notes 3 notes

up
4
codeguru at crazyprogrammer dot cba dot pl
6 years ago
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)
)
up
4
elloromtz at gmail dot com
4 years ago
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
?>
up
-1
bobvin at pillars dot net
3 years ago
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);
?>
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