View source for Potential backward compatibility issues in Joomla 4

=== Language === <!--T:151-->
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* The functions setTransliterator, setPluralSuffixesCallback, setIgnoredSearchWordsCallback, setLowerLimitSearchWordCallback, setUpperLimitSearchWordCallback and setSearchDisplayedCharactersNumberCallback are now typehinted to require a callable.
* The <tt>"_QQ_"</tt> placeholder for double quotes has been removed (this only existed to work around an old PHP Bug that has been fixed). Escape double quotes if required (i.e. <tt>\"</tt>)
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* The format for language file names has been changes to ease the work in 3rd party translation tools (such as Crowdin). INI language files no longer have to contain the language code (i.e. en-GB.com_contact.ini => com_contact.ini), in this case the special case of en-GB.ini has been renamed to ''joomla.ini'' in the core language pack. en-GB.xml has been named langmetadata.xml. There is a b/c layer that will continue to read the old Joomla 3 file names throughout Joomla 4.</translate>
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* \Joomla\CMS\Language\Multilanguage::getSiteLangs has been removed. Use \Joomla\CMS\Language\LanguageHelper::getInstalledLanguages(0) instead</translate>
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* JLanguage::exists has been removed. Use Joomla\CMS\Language\LanguageHelper::exists instead.</translate>
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* The wrapper classes JTextWrapper, LanguageHelperWrapper and TransliterateWrapper have been removed. Continue to use the static methods they wrapped.</translate>
<translate><!--T:289--> * The pdf_fonts handling/support for language packs (<code>language/pdf_fonts</code>) has been removed from the language installer ([https://github.com/joomla/joomla-cms/pull/31288 see GitHub PR #31288]).</translate>

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