How to use the mb_detect_encoding function in PHP

This article mainly introduces the detailed explanation of how to use the mb_detect_encoding function in PHP, including the conversion and judgment of string encoding and the solution to the error of Call to undefined function mb_detect_encoding(). Friends in need can refer to it

php You can use the mb_detect_encoding() function to determine the encoding of a string.

When using the mb_detect_encoding function in php for encoding identification, many people have encountered the problem of incorrect encoding, such as GB2312 and UTF-8, or UTF-8 and GBK (mainly here Regarding the judgment of cp936), it is said on the Internet that mb_detect_encoding will misjudge due to short characters.

The code is as follows:

$encode = mb_detect_encoding($keytitle, array("ASCII","UTF-8","GB2312","GBK","BIG5"));
if($encode == "UTF-8"){
  $keytitle = iconv("UTF-8","GBK",$keytitle);
}

The function of this code is to detect whether the encoding of the string is UTF-8. If so, Convert to GBK.
But when $keytitle = “оƬ”;. The detection result is UTF-8. This bug is not actually a bug, and you should not rely too much on mb_detect_encoding when writing programs. When the string is short, the detection results are likely to be biased.
Solution, the code is as follows:

$encode = mb_detect_encoding($keytitle, array("ASCII","GB2312","GBK","UTF-8");

The three parameters are: the input variable to be detected, the detection order of the encoding method (once is true, the following will be automatically ignored), strict mode adjusts the order of encoding detection, putting the greatest possibility first, thus reducing the chance of incorrect conversion.
Generally, gb2312 should be sorted first. When there are GBK and UTF-8, the commonly used ones need to be sorted first.

Conversion and judgment of PHP string encoding

Conversion between GBK and UTF-8 encoding is a very disgusting thing. For example, json_encode in PHP itself does not work at all. Supports GBK format encoding. There are two library functions that can support encoding conversion. The iconv function that usually comes to mind is very fun to use:
iconv('GBK', 'UTF-8//IGNORE', 'test string'); //Convert the string from GBK encoding to UTF-8 encoding

But iconv can only solve the situation where the encoding is known in advance. If the string encoding is unknown, you need to detect its encoding first, which may be used at this time mb_string extension library:
mb_detect_encoding('test string');

However, mb_detect_encoding has a flaw, and inaccurate judgment often occurs. Maybe this can be solved:

// 使用 iconv 转换并判断是否等值，效率不高
function is_utf8 ($str) {
  if ($str === iconv('UTF-8', 'UTF-8//IGNORE', $str)) {
    return 'UTF-8';
  }
}
// 多种编码的情况
function detect_encoding ($str) {
  foreach (array('GBK', 'UTF-8') as $v) {
    if ($str === iconv($v, $v . '//IGNORE', $str)) {
      return $v;
    }
  }
}

After obtaining the string encoding information through the above method, you can use iconv or mb_convert_encoding to convert the encoding.

Call to undefined function mb_detect_encoding() error solution

Under Windows system:
1. Fatal error: Call to undefined function: iconv() in C:\Program Files\AppServ\www\...\xxx.php on line 82
There is an iconv() function in php for character encoding conversion
In the php.ini file There is also a statement like extension=php_iconv.dll
to ensure the normal use of this function
If there is a semicolon in front of extension=php_iconv.dll in the php.ini file
It means it is commented out, if it exists The semicolon must be removed and the server restarted.
Run the program again to solve the problem.

2. Fatal error: Call to undefined function: mb_detect_encoding() in C:\Program Files\AppServ\www\.. .\xxx.php on line 1355
1. Find the php extension directory (the path of my php extension directory is: C:\Program Files\AppServ\php\extensions)
Find php_mbstring.dll under the extensions directory file,
2. Copy the php_mbstring.dll file to the directory where the php.ini file is located (the directory where my php.ini file is located: C:\WINDOWS)
3. Open php with Notepad. ini file, use the shortcut key Ctrl F to search for extension=php_mbstring.dll
4. If extension=php_mbstring.dll exists in the php.ini file, remove the semicolon in front of the extension in the line,
If it does not exist, just Add extension=php_mbstring.dll to the next line of other extension=...,
Finally, remember to save the php.ini file
5. Restart your Apache server

I just discovered that php_mbstring is not actually copied. The dll file can also be moved to the directory where php.ini is located.

Under Linux system:

When the following problem occurs:

PHP 1. {main} () /home/xu/web/whois/ab.cn.php:0
PHP 2. base_func->is_exist() /home/xu/web/whois/ab.cn.php:21
PHP 3. strftime() /home/xu/web/whois/whois.mysql.php:46
ab.cnis existdf250b2156c434f3390392d09b1c9563PHP Fatal error: Call to undefined function mb_detect_encoding() in /home/xu /web/whois/whois.main.php on line 98
After searching for various information on the Internet, I found out that the php plug-in php-mbstring was not installed (some students may not have enabled this plug-in in php.ini ), write this paragraph for notes.

First use yum or apt to install mbstring.so, use the command: yum install php-mbstring or apt-get install php-mbstring (ubuntu users are best to use apt-cache search mbstring to search before installing. The software name may be wrong)

Then modify php.ini: execute vim /etc/php.ini and add extension="/usr/lib/php/modules/mbstring.so" content. The following paths may be different. They are stored according to mbstring.so Just make the corresponding changes to the directory. Generally there is no need to change it.

The above is the entire content of this article. I hope it will be helpful to everyone's study. For more related content, please pay attention to the PHP Chinese website!

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