String Functions
PHP Manual

substr_compare

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

Description

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

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
?>

See Also

  • strncmp