note 129132 added to function.mb-substr

Here is an example demonstrating the difference between substr and mb_substr functions: 1- When working with non UTF-8 characters, both functions behave the same and give the same output: $str = 'abcdef'; echo substr($s, 0, 3); // abc echo mb_substr($s, 0, 3); // abc 2- When working with UTF-8 characters, each function will behave differently and give a different result: 2.A- The 'substr' function works on the byte-level and with single-byte encoded characters only (doesn't support multibyte encoding). For example: $str_utf8 = utf8_encode("déjà_vu"); If we do this: echo substr($str_utf8, 0, 3); // dé echo substr($str_utf8, 0, 2); // d� => That's because the special character "é" (and "à") is internally coded with two bytes: PHP will start reading the first byte at index 0, which represents d, then move to the second byte, which is a part of the two-byte encoding of the character é , and since the length is set to 2, PHP will stop here and doesn't continue reading the third byte, so it doesn't recognize the character é and prints � instead of é. 2.B- The 'mb_substr' function works on the character-level and supports multibyte encoded characters. This means, PHP counts the number of characters only and doesn't take into consideration the number of bytes of their encoding, for example: $str_utf8 = utf8_encode("déjà_vu"); echo mb_substr($str_utf8, 0, 4, "UTF-8"); // Déjà echo mb_substr($str_utf8, 1, 4, "UTF-8"); // éjà_ echo mb_substr($str_utf8, 6, 4, "UTF-8"); // u echo mb_substr($str_utf8, 7, 4, "UTF-8"); // '' echo mb_substr($str_utf8, -2, "UTF-8"); // vu echo mb_substr($str_utf8, -2, 1, "UTF-8"); // v echo mb_substr($str_utf8, -2, 3, "UTF-8"); // vu ---- Server IP: 45.112.84.4 Probable Submitter: 45.91.157.134 (proxied: 105.110.31.55) ---- Manual Page -- https://php.net/manual/en/function.mb-substr.php Edit -- https://main.php.net/note/edit/129132 Del: integrated -- https://main.php.net/note/delete/129132/integrated Del: useless -- https://main.php.net/note/delete/129132/useless Del: bad code -- https://main.php.net/note/delete/129132/bad+code Del: spam -- https://main.php.net/note/delete/129132/spam Del: non-english -- https://main.php.net/note/delete/129132/non-english Del: in docs -- https://main.php.net/note/delete/129132/in+docs Del: other reasons-- https://main.php.net/note/delete/129132 Reject -- https://main.php.net/note/reject/129132 Search -- https://main.php.net/manage/user-notes.php