How to check the charset of string?

Question

How do I check if the charset of a string is UTF8?

Answer 1

Better yet, use both of the above solutions.

function isUtf8($string) {
    if (function_exists("mb_check_encoding") && is_callable("mb_check_encoding")) {
        return mb_check_encoding($string, 'UTF8');
    }

    return preg_match('%^(?:
          [\x09\x0A\x0D\x20-\x7E]            # ASCII
        | [\xC2-\xDF][\x80-\xBF]             # non-overlong 2-byte
        |  \xE0[\xA0-\xBF][\x80-\xBF]        # excluding overlongs
        | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}  # straight 3-byte
        |  \xED[\x80-\x9F][\x80-\xBF]        # excluding surrogates
        |  \xF0[\x90-\xBF][\x80-\xBF]{2}     # planes 1-3
        | [\xF1-\xF3][\x80-\xBF]{3}          # planes 4-15
        |  \xF4[\x80-\x8F][\x80-\xBF]{2}     # plane 16
    )*$%xs', $string);

} 

Answer 2

function is_utf8($string) {   
return preg_match('%^(?:  
[\x09\x0A\x0D\x20-\x7E] # ASCII  
| [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte  
| \xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs  
| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte  
| \xED[\x80-\x9F][\x80-\xBF] # excluding surrogates  
| \xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3  
| [\xF1-\xF3][\x80-\xBF]{3} # planes 4-15  
| \xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16  
)*$%xs', $string);   

}

I have checked. This function is effective.