How to do error logging in CodeIgniter (PHP)

I want error logging in PHP CodeIgniter. How do I enable error logging?

I have some questions:

• What are all the steps to log an error?
  
• How is an error log file created?
  
• How to push the error message into log file (whenever an error occurs)?
  
• How do you e-mail that error to an email address?
  

Please read:

CodeIgniter 4 User Guide - Error Handling

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

See https://codeigniter4.github.io/CodeIgnit...gging.html

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper

CodeIgniter has some error logging functions built in.

Make your /application/logs folder writable
In /application/config/config.php set
$config['log_threshold'] = 1;
or use a higher number, depending on how much detail you want in your logs
Use log_message('error', 'Some variable did not contain a value.');
To send an email you need to extend the core CI_Exceptions class method log_exceptions(). You can do this yourself or use this. More info on extending the core here