strtoupper()

(PHP 4, PHP 5, PHP 7)

将字符串转化为大写

说明

将$string中所有的字母字符转换为大写并返回。

注意“字母”与当前所在区域有关。例如，在默认的“C”区域，字符 umlaut-a（ä）就不会被转换。

参数

输入字符串。

返回值

返回转换后的大写字符串。

范例

Example #1strtoupper()范例

注释

Note:此函数可安全用于二进制对象。

参见

• strtolower()将字符串转化为小写
• ucfirst()将字符串的首字母转换为大写
• ucwords()将字符串中每个单词的首字母转换为大写
• mb_strtoupper()使字符串大写

One might think that setting the correct locale would do the trick with for example german umlauts, but this is not the case. You have to use mb_strtoupper() instead:

something I myself first not thought about:
if there are any html entities (named entities) in your string, strtoupper will turn all letters within this entities to upper case, too. So if you want to manipulate a string with strtoupper it should contain only unicode entities (if ever).

If you only need to extend the conversion by the characters of a certain language, it's possible to control this using an environment variable to change the locale:
setlocale(LC_CTYPE, "de_DE");

It has been mentioned in a previous comment that all you need to do to let PHP's strtoupper() do the conversion - instead of writing more or less complicated functions yourself - is to specify the locale in which you're doing the case conversion:

It is important to note that setlocale() will silently fail if it can't find the specified locale on your system, so *always* check its return value. Try different spellings: using "de_AT" as an example, there are various combinations that may or may not work for you: "de", "de_AT.utf8", "de_AT.iso-8859-1", "de_AT.latin1", "de_AT@euro", etc).
If you can't find an appropriate locale setting, check your system configuration (locales are a system-wide setting, PHP gets them from the OS). On Windows, locales can be set from the Control Panel; on Linux it depends on your distribution. You can try "sudo dpkg-reconfigure locales" on Debian-based distros, or configure them manually. On Ubuntu Dapper, I had to copy entries over from /usr/share/i18n/SUPPORTED to /var/lib/locales/supported.d/local, then do the dpkg-reconfigure.
After you're done, restart the web server.
That said, there are special cases where you want to do the conversion manually. In German, for example, the letter 'ß' (szlig) only exists as a lower-case character, and so doesn't get converted by strtoupper. The convential way to express a 'ß' in an uppercase string is "SS". This function will take care of this exception (for Latin1 and most of Latin9, at least):

// 2005/5/30 Justin
  // Chinese_Traditional toupper
  function CT_to_upper($string)
  {    
    $isChineseStart = false;
    
     $new_string = "";
     $i = 0;
     while($i 

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