Why don't php errors end up in Apache's error_log?

Question

PHP

Good day.
Prompt, please, on such question: is apache and php.
The apache config contains the following settings:

ErrorLog logs/error_log
LogLevel warn
CustomLog logs/access_log combined

In php.ini php errors are not getting into the apache log. What do you need to do to get in?
прописан error_log = /var/log/php_error.log