PHP Manual: substr

Description

function substr_compare(
    string $haystack,
    string $needle,
    int $offset,
    ?int $length = null,
    bool $case_insensitive = false
): int

substr_compare() compares haystack from position offset with needle up to length characters.

Parameters

haystack: The main string being compared.
needle: The secondary string being compared.
offset: The start position for the comparison. If negative, it starts counting from the end of the string.
length: The length of the comparison. The default value is the largest of the length of the needle compared to the length of haystack minus the offset.
case_insensitive: If case_insensitive is true, comparison is case insensitive.

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.

Errors/Exceptions

Throws a ValueError if offset is greater than the length of haystack and length is not 0, or if length is less than 0.

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.
8.0.0	Now throws a ValueError if `offset` is out of range or `length` is negative. Previously, an `E_WARNING` was raised and `false` was returned.
8.0.0	`length` is nullable now.
7.2.18, 7.3.5	`offset` may now be equal to the length of `haystack`.

Examples

Example #1 A substr_compare() example

<?php
echo substr_compare("abcde", "bc", 1, 2), PHP_EOL; // 0
echo substr_compare("abcde", "de", -2, 2), PHP_EOL; // 0
echo substr_compare("abcde", "bcg", 1, 2), PHP_EOL; // 0
echo substr_compare("abcde", "BC", 1, 2, true), PHP_EOL; // 0
echo substr_compare("abcde", "bc", 1, 3), PHP_EOL; // 1
echo substr_compare("abcde", "cd", 1, 2), PHP_EOL; // -1
echo substr_compare("abcde", "abc", 5, 1), PHP_EOL; // -1
?>