(PHP 4 >= 4.3.0, PHP 5)
mb_strtolower — Make a string lowercase
Returns str with all alphabetic characters converted to lowercase.
The string being lowercased.
encoding 参数为字符编码。如果省略，则使用内部字符编码。
str with all alphabetic characters converted to lowercase.
For more information about the Unicode properties, please see » http://www.unicode.org/unicode/reports/tr21/.
By contrast to strtolower(), 'alphabetic' is determined by the Unicode character properties. Thus the behaviour of this function is not affected by locale settings and it can convert any characters that have 'alphabetic' property, such as A-umlaut (Ä).
Example #1 mb_strtolower() example
<?php
$str = "Mary Had A Little Lamb and She LOVED It So";
$str = mb_strtolower($str);
echo $str; // Prints mary had a little lamb and she loved it so
?>
Example #2 mb_strtolower() example with non-Latin UTF-8 text
<?php
$str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
$str = mb_strtolower($str, 'UTF-8');
echo $str; // Prints τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός
?>