The text encoding output by the PHPfwrite function is ANSI, brother, I need UTF-8

The text encoding output by the PHP fwrite function is ANSI, and I need UTF-8

$xmlCOntent= ‘Assume that this string is a well-formed XML text message that includes special characters’;

// mb_detect_encoding($xmlContent) is used here; the output result is UTF-8

// Write file
$xmlFile = fopen(“file.xml” ,”w”);
fwrite($xmlFile,$xmlContent);
fclose($xmlFile);

In addition, the referenced global configuration file is as follows Set header(“Content-Type:text/html; charset=UTF-8”);

Open the file.xml file with Notepad and save it as. The ANSI encoding is displayed

I need to save file.xml as UTF-8, how to change the code?

——Solution——————–
Indeed, I have tested your code. No problem on my end. .
Check it carefully. PHP file, echo mb_detect_encoding($xmlContent); whether it is utf-8