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IntlChar::tolower

(PHP 7, PHP 8)

IntlChar::tolowerMake Unicode character lowercase

説明

public static IntlChar::tolower(mixed $codepoint): mixed

The given character is mapped to its lowercase equivalent. If the character has no lowercase equivalent, the original character itself is returned.

パラメータ

codepoint

コードポイントを表す int 型の値 (例: U+2603 SNOWMAN を表す 0x2603)、あるいは UTF-8 文字列としてエンコードされた文字 (例: "\u{2603}")。

返り値

Returns the Simple_Lowercase_Mapping of the code point, if any; otherwise the code point itself.

戻り値の型は int になります。ただし、コードポイントを UTF-8 文字列で渡した場合は別で、その場合の返り値の型は文字列になります。

例1 さまざまなコードポイントの例

<?php
var_dump
(IntlChar::tolower("A"));
var_dump(IntlChar::tolower("a"));
var_dump(IntlChar::tolower("Φ"));
var_dump(IntlChar::tolower("φ"));
var_dump(IntlChar::tolower("1"));
var_dump(IntlChar::tolower(ord("A")));
var_dump(IntlChar::tolower(ord("a")));
?>

上の例の出力は以下となります。

string(1) "a"
string(1) "a"
string(2) "φ"
string(2) "φ"
string(1) "1"
int(97)
int(97)

参考

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User Contributed Notes 2 notes

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0
Patanjali
1 year ago
The other function I wrote to replace mb_strtolower may not work properly, as it erroneously equated graphemes with codepoints.

tolower, like many IntlChar methods, works specifically on codepoints, so requires a codepoint iterator to isolate each.

Also, because in tolower, if there is no lowercase version of the codepoint, the supplied one is returned, so there is no need to specially test for alphabetic codepoints before conversion.

<?php
function u_tolower($text=''){
// if blank, return blank (don't waste CPU cycles)
if($text==''){return'';}

// create the codepoint break iterator to identify the start of each codepoint
$iterator=IntlBreakIterator::createCodePointInstance();

// load the text
$iterator->setText($text);

// using a parts iterator to extract each codepoint itself, convert and append it to the new string
$newtext='';
foreach(
$iterator->getPartsIterator() as $codepoint){$newtext.=IntlChar::tolower($codepoint);}

// return converted text
return $newtext;
}
?>
up
-1
Patanjali
1 year ago
A function to convert a Unicode string to lowercase, directly replacing mb_strtolower, by converting one grapheme at a time:

<?php
function u_tolower($text=''){
// if blank, return blank (don't waste CPU cycles)
if($text==''){return '';}

// for each grapheme
$str='';
for(
$i=0;$i<grapheme_strlen($text);$i++){
 
// add to string if alpha, else as is
 
$char=grapheme_substr($text,$i,1);
 
$str.=(IntlChar::isalnum($char)?IntlChar::tolower($char):$char);
}

// return converted text
return $str;
}
?>
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