PHP 8 reference · String Functions

PHP strnatcmp() Function

Compare strings in natural order, so "img2" comes before "img10" the way people expect. Case-sensitive.

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Syntax

strnatcmp(string $string1, string $string2): int

Parameter	Description
`string1`	The first string.
`string2`	The second string.

0 if equal; negative or positive otherwise.

Natural vs byte orderTry it yourself

<?php
var_dump(strcmp("img10", "img2") < 0);    // byte order
var_dump(strnatcmp("img10", "img2") < 0); // natural order

Output

bool(true)
bool(false)

Sort file namesTry it yourself

<?php
$files = ["file10.txt", "file2.txt", "file1.txt"];
usort($files, "strnatcmp");
print_r($files);

Output

Array
(
    [0] => file1.txt
    [1] => file2.txt
    [2] => file10.txt
)

Version	Change
PHP 4.0	Added

strnatcasecmp() · Compare strings in natural order ("a2" before "a10") while ignoring upper and lower case.
natsort() · Sort an array in natural order, so "img2" comes before "img10", keeping keys. Case-sensitive.
strcmp() · Compare two strings byte by byte, case-sensitively. Returns 0 when equal, less than 0 or more than 0 otherwise.
PHP Strings · tutorial