(PHP 5, PHP 7, PHP 8)
substr_compare — Binary safe comparison of two strings from an offset, up to length characters
substr_compare( string $haystack, string $needle, int $offset, ?int $length = null, bool $case_insensitive = false ): int
substr_compare() compares haystack from position offset with needle up to length characters.
haystackThe main string being compared.
needleThe secondary string being compared.
offsetThe start position for the comparison. If negative, it starts counting from the end of the string.
length The length of the comparison. The default value is the largest of the length of the needle compared to the length of haystack minus the offset.
case_insensitive If case_insensitive is true, comparison is case insensitive.
Returns a value less than 0 if string1 is less than string2; a value greater than 0 if string1 is greater than string2, and 0 if they are equal. No particular meaning can be reliably inferred from the value aside from its sign.
If offset is equal to (prior to PHP 7.2.18, 7.3.5) or greater than the length of haystack, or the length is set and is less than 0, substr_compare() prints a warning and returns false.
| Version | Description |
|---|---|
| 8.2.0 | This function is no longer guaranteed to return strlen($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. |
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
?>
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https://www.php.net/manual/en/function.substr-compare.php