PHP 8 reference · String Functions

PHP strcmp() Function

Compare two strings byte by byte, case-sensitively. Returns 0 when equal, less than 0 or more than 0 otherwise.

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Syntax

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

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

0 if equal; a negative number if string1 sorts first; a positive number otherwise.

Compare stringsTry it yourself

<?php
var_dump(strcmp("apple", "apple"));
var_dump(strcmp("apple", "banana") < 0);
var_dump(strcmp("a", "A") > 0); // lowercase sorts after uppercase

Output

int(0)
bool(true)
bool(true)

Sort with strcmp()Try it yourself

<?php
$names = ["bob", "Alice", "carol"];
usort($names, "strcmp");
print_r($names);

Output

Array
(
    [0] => Alice
    [1] => bob
    [2] => carol
)

Only the sign of the result matters. Test < 0, === 0 or > 0, not === -1.
For equality, $a === $b is clearer. Use hash_equals() to compare secrets such as tokens.

Version	Change
PHP 4.0	Added

strcasecmp() · Compare two strings without caring about ASCII upper and lower case. Returns 0 if they match.
strncmp() · Compare only the first n bytes of two strings, case-sensitively. Handy for checking a prefix in older code.
strnatcmp() · Compare strings in natural order, so "img2" comes before "img10" the way people expect. Case-sensitive.
usort() · Sort an array's values with your own comparison function, in place. Keys are discarded. Use <=> for easy comparisons.
PHP Strings · tutorial

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