Unicode case mapping

Case mapping changes letters between uppercase, lowercase, and title case. The Unicode standard defines simple and full mappings:

Simple mapping maps one code point to one code point.
Full mapping may map one code point to multiple code points.

For example, full uppercase mapping converts the German ß to SS, while simple mapping leaves it as ß. Case Converter uses full mapping by default.

use Jawira\CaseConverter\Convert;

$value = new Convert('Straße');

$value->toUpper(); // STRASSE
$value->forceSimpleCaseMapping()->toUpper(); // STRAßE

forceSimpleCaseMapping() returns the same object. It affects subsequent conversion calls on that object; it does not change the detected words or the source string.

Locale-specific behavior

Case Converter uses PHP's mb_convert_case() with UTF-8. The library does not accept a locale setting, so locale-specific casing rules, such as Turkish dotted and dotless i, are not selected based on the user's locale.

Evolution of Case-Mapping in PHP

PHP 7.3 introduced full case-mapping, you can have one-to-many character mapping. In practice this means than you can have different results depending on your PHP version.

Internally Case-Converter uses mb_convert_case () . This function works in conjunction with specific constants to tell what action to perform. For example:

mb_convert_case('Foo', MB_CASE_UPPER); // FOO

Prior to PHP 7.3, these were the available constants and their use:

Constant	Meaning
MB_CASE_UPPER	Performs simple upper-case fold conversion.
MB_CASE_LOWER	Performs simple lower-case fold conversion.
MB_CASE_TITLE	Performs simple title-case fold conversion.

But from PHP 7.3, new constants were added and their meaning changed:

Constant	Meaning
MB_CASE_UPPER	Performs a full upper-case folding.
MB_CASE_LOWER	Performs a full lower-case folding.
MB_CASE_TITLE	Performs a full title-case conversion.
MB_CASE_UPPER_SIMPLE	Performs simple upper-case fold conversion.
MB_CASE_LOWER_SIMPLE	Performs simple lower-case fold conversion.
MB_CASE_TITLE_SIMPLE	Performs simple title-case fold conversion.

Unicode case mapping

Locale-specific behavior

Evolution of Case-Mapping in PHP

Further reading