W3cubDocs

/PHP

strncmp

(PHP 4, PHP 5, PHP 7, PHP 8)

strncmp — Binary safe string comparison of the first n characters

Description

strncmp(string $string1, string $string2, int $length): int

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

string1

The first string.

string2

The second string.

length

Number of characters to use in the comparison.

Return Values

Returns a value less than 0 if string1 is less than string2; a value greater than 0 if string1 is greater than string2, and 0 if they are equal. No particular meaning can be reliably inferred from the value aside from its sign.

Changelog

Version Description
8.2.0 This function is no longer guaranteed to return strlen($string1) - strlen($string2) when string lengths are not equal, but may now return -1 or 1 instead.

Examples

Example #1 strncmp() example

<?php

$var1 = 'Hello John';
$var2 = 'Hello Doe';
if (strncmp($var1, $var2, 5) === 0) {
    echo 'First 5 characters of $var1 and $var2 are equal in a case-sensitive string comparison';
}
?>

See Also

  • strncasecmp() - Binary safe case-insensitive string comparison of the first n characters
  • preg_match() - Perform a regular expression match
  • substr_compare() - Binary safe comparison of two strings from an offset, up to length characters
  • strcmp() - Binary safe string comparison
  • strstr() - Find the first occurrence of a string
  • substr() - Return part of a string

© 1997–2025 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.strncmp.php