Error: undefined index

Hello, when you enter the password on the site, for the place of Latin letters are shown what kind of hieroglyphs.
and an error is displayed:
Attention: unspecified index: mysql_host in / storage / ssd2 / 523/6708523 / public_html / install / install.php on line 96

if ($ _POST ["mysql_host"] && $ _POST ["mysql_user"] 
&& $ _POST ["mysql_db"] && $ POST
["mysql_charset"]) {
$ secretsbuild = '<?
$ mysql_host = "'. $ _ POST [" mysql_host "].'";
$ mysql_user = "'. $ _ POST [" mysql_user "].'";
$ mysql_pass = "'. $ _ POST [" mysql_pass "].'";
$ mysql_db = "'. $ _ POST [" mysql_db "].'";
$ mysql_charset = "'. $ _ POST [" mysql_charset "].'";
?> ';
$ secrets = fopen ("./ include / secrets.php", "w");
fwrite ($ secrets, $ secretsbuild);
fclose ($ secrets);
?>

Can I fix it to show it in Latin letters?

Hi !

when you enter the password on the site, for the place of Latin letters are shown what kind of hieroglyphs.

Try this tutorial: How to fix the character set (charset) issue

Attention: unspecified index: mysql_host

Make sure $_POST['mysql_host'] is defined properly…

Thanks, the problem is already solved.
But there was another problem … When I connected to the database, tables were loaded, but one table writes error: Invalid default value for ‘subject’

How do I start an error search?

In what circumstances are you receiving that error? And what is the URL on which you are receiving it?