Case-Mapping

Introduction

>Case mapping or case conversion is a process whereby strings are converted to a particular form?uppercase, lowercase, or titlecase?possibly for display to the user.

PHP always performed _Simple Case-Mapping_, this is map one-to-one character mapping. For example, one _lower case_ character is converter to one _upper case_ character.

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.

$german = new Convert('Straße');

echo $german->toUpper();
// Produces STRAßE on PHP 7.2
// Produces STRASSE on PHP 7.3

Please note that _Full Case-Mapping_ is locale dependent:

// Turkish (requires appropriate locale)
$tur = new Convert('istambul');     
echo $tur->toTrain();   // output: ?stanbul

Forcing _Simple Case-Mapping_

As told before, _Full Case-Mapping_ is only available on PHP 7.3 and newer.

The following code snippet is executed on PHP 7.3:

// German
$ger = new Convert('Straße');
echo $ger->toUpper();    // output: STRASSE

To force _Simple Case-Mapping_ you have to call ->forceSimpleCaseMapping():

// German
$ger = new Convert('Straße');
$ger->forceSimpleCaseMapping();
echo $ger->toUpper();    // output: STRAßE

Please note ->forceSimpleCaseMapping() has no effect on _PHP 7.1_ and _PHP 7.2_ as these version can only perform _Simple Case-Mapping_.

Technical details

Internally Case-Converter uses [mb_convert_case()], this function uses the following constants:

• MB_CASE_LOWER
• MB_CASE_TITLE
• MB_CASE_UPPER

The problem is that, Before _PHP 7.3_, these constants perform simple case-mapping and after _PHP 7.3_ perform full case-mapping.

If you want to maintain the old functionality after _PHP 7.3_ you have to call ->forceSimpleCaseMapping():

// German
$ger = new Convert('Straße');
$ger->forceSimpleCaseMapping();
echo $ger->toUpper();    // output: STRASSE

*

IMHO this is a _breaking change_, PHP people should have keep untouched old constants and create new ones for [Full Case-Mapping], for example: MB_CASE_LOWER_FULL, MB_CASE_TITLE_FULL, and MB_CASE_UPPER_FULL (please note these variables do not exist).

[Full Case-Mapping]: https://www.php.net/manual/en/migration73.new-features.php#migration73.new-features.mbstring.case-mapping-folding [mb_convert_case()]: https://www.php.net/manual/en/function.mb-convert-case.php