PHP Manual: mb_convert

Description

function mb_convert_case(string $string, int $mode, ?string $encoding = null): string

Performs case folding on a string, converted in the way specified by mode.

Parameters

string: The string being converted.
mode: The mode of the conversion. It can be one of MB_CASE_UPPER, MB_CASE_LOWER, MB_CASE_TITLE, MB_CASE_FOLD, MB_CASE_UPPER_SIMPLE, MB_CASE_LOWER_SIMPLE, MB_CASE_TITLE_SIMPLE, MB_CASE_FOLD_SIMPLE.
encoding: The encoding parameter is the character encoding. If it is omitted or null, the internal character encoding value will be used.

Return Values

A case folded version of string converted in the way specified by mode.

Errors/Exceptions

As of PHP 8.0.0, a ValueError is thrown if encoding is an invalid encoding. Prior to PHP 8.0.0, an E_WARNING was emitted instead.

Changelog

Version	Description
8.3.0	Implemented conditional casing rules for the Greek letter sigma which only apply to `MB_CASE_LOWER` and `MB_CASE_TITLE` modes, not to `MB_CASE_LOWER_SIMPLE` and `MB_CASE_TITLE_SIMPLE`.
8.0.0	Now throws a ValueError if `encoding` is an invalid encoding. Previously, an `E_WARNING` was emitted and `false` was returned.
7.3.0	Added support for `MB_CASE_FOLD`, `MB_CASE_UPPER_SIMPLE`, `MB_CASE_LOWER_SIMPLE`, `MB_CASE_TITLE_SIMPLE`, and `MB_CASE_FOLD_SIMPLE` as `mode`.

Examples

Example #1 mb_convert_case() example

<?php
$str = "mary had a Little lamb and she loved it so";
$str = mb_convert_case($str, MB_CASE_UPPER, "UTF-8");
echo $str, PHP_EOL;
$str = mb_convert_case($str, MB_CASE_TITLE, "UTF-8");
echo $str, PHP_EOL;
?>

Example #2 mb_convert_case() example with non-Latin UTF-8 text

<?php
$str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
$str = mb_convert_case($str, MB_CASE_UPPER, "UTF-8");
echo $str, PHP_EOL;
$str = mb_convert_case($str, MB_CASE_TITLE, "UTF-8");
echo $str, PHP_EOL;
?>

Notes

By contrast to the standard case folding functions such as strtolower() and strtoupper(), case folding is performed on the basis of the Unicode character properties. Thus the behaviour of this function is not affected by locale settings and it can convert any characters that have 'alphabetic' property, such a-umlaut (ä).

For more information about the Unicode properties, please see » https://www.unicode.org/reports/tr21/.

mb_convert_case