What is the usage of iconv in PHP?

In PHP, the function iconv() is used for converting between character sets. Its basic usage is as follows:

Convert the string from one character encoding to another.

Explanation of parameters:

1. $in_charset: Character set of the input string.
2. $out_charset: character set of the output string.
3. $str: The string to be converted.

Return value:
Return the transformed string.

例子：例如

$str = "你好，世界！";
$convertedStr = iconv("UTF-8", "GBK", $str);
echo $convertedStr; // 输出：浣犲ソ锛堟垜鍥�

$convertedStr2 = iconv("GBK", "UTF-8", $convertedStr);
echo $convertedStr2; // 输出：你好，世界！

In the examples above, the UTF-8 encoded string is first converted to a GBK encoded string, and then the converted string is converted back to UTF-8 encoding.

Important points to note:

1. When dealing with character set conversions, errors may occur in the iconv() function, which can be ignored by setting the error_reporting() function.
2. If there are characters that cannot be converted during the conversion process, the iconv() function will by default replace those characters with a question mark (?). Setting the fourth parameter of the iconv() function allows for specifying a different way to replace these characters.

For further information on how to use and the parameters of the iconv() function, please refer to the official PHP documentation.