How can I disable notices and warnings in PHP within the .htaccess file?

It is probably not the best thing to do. You need to at least check out your PHP error log for things going wrong ;)

# PHP error handling for development servers
php_flag display_startup_errors off
php_flag display_errors off
php_flag html_errors off
php_flag log_errors on
php_flag ignore_repeated_errors off
php_flag ignore_repeated_source off
php_flag report_memleaks on
php_flag track_errors on
php_value docref_root 0
php_value docref_ext 0
php_value error_log /home/path/public_html/domain/PHP_errors.log
php_value error_reporting -1
php_value log_errors_max_len 0

If you are in a shared hosting plan that doesn't have PHP installed as a module you will get a 500 server error when adding those flags to the .htaccess file.

But you can add the line

ini_set('display_errors','off');

on top of your .php file and it should work without any errors.

Try:

php_value error_reporting 2039

Fortes is right, thank you.

When you have a shared hosting it is usual to obtain an 500 server error.

I have a website with Joomla and I added to the index.php:

ini_set('display_errors','off');

The error line showed in my website disappeared.