PHP 8 reference · String Functions

PHP strnatcasecmp() Function

Compare strings in natural order ("a2" before "a10") while ignoring upper and lower case.

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Syntax

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

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

0 if equal; negative or positive otherwise.

Natural, case-insensitiveTry it yourself

<?php
var_dump(strnatcasecmp("Chapter10", "chapter9") > 0);

Output

bool(true)

Sort mixed-case namesTry it yourself

<?php
$items = ["Item20", "item3", "ITEM100"];
usort($items, "strnatcasecmp");
print_r($items);

Output

Array
(
    [0] => item3
    [1] => Item20
    [2] => ITEM100
)

Version	Change
PHP 4.0	Added

strnatcmp() · Compare strings in natural order, so "img2" comes before "img10" the way people expect. Case-sensitive.
natcasesort() · Sort an array in natural order while ignoring case, keeping keys. "Item2" comes before "item10".
strcasecmp() · Compare two strings without caring about ASCII upper and lower case. Returns 0 if they match.
PHP Strings · tutorial