Description:
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---
From manual page: https://php.net/function.str-ireplace
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Function str_ireplace fails to replace diacritics characters if case (lower or upper) of search pattern does not match case of characters in subject string. Affected languages: french, russian, german, spanish, etc. Short php-script sample provided below.



Test script:
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<?php
// French
// Result: 1À 2Â 3Ä 4Æ
// Expect: 11 22 33 44
echo str_ireplace(['à', 'â', 'ä', 'æ'], ['1', '2', '3', '4'], 'àÀ â äÄ æÆ') . PHP_EOL;
// Result: à1 â2 ä3 æ4
// Expect: 11 22 33 44
echo str_ireplace(['À', 'Â', 'Ä', 'Æ'], ['1', '2', '3', '4'], 'àÀ â äÄ æÆ') . PHP_EOL;

// Russian
// Result: 1Ё 2Й
// Expect: 11 22
echo str_ireplace(['ё', 'й'], ['1', '2'], 'ёЁ йЙ') . PHP_EOL;
// Result: ё1 й2
// Expect: 11 22
echo str_ireplace(['Ё', 'Й'], ['1', '2'], 'ёЁ йЙ') . PHP_EOL;