PHP Manual
String Functions
Binary safe comparison of two strings from an offset, up to length characters

substr_compare

(PHP 5, PHP 7, PHP 8)

substr_compare — Binary safe comparison of two strings from an offset, up to length characters

Description

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.

If offset is equal to (prior to PHP 7.2.18, 7.3.5) or greater than the length of haystack, or the length is set and is less than 0, substr_compare() prints a warning and returns false.

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	`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
?>