MKDIR() Permission Denied Codeigniter 3

CodeIgniter has some error logging functions built in. You can log any errors to system log with function log_message

Also you can set log level in your application/config/config.phphere is the sample settings:

/*|--------------------------------------------------------------------------| Error Logging Threshold|--------------------------------------------------------------------------|       0                           = Disables logging, Error logging TURNED OFF|       1                           = Error Messages (including PHP errors)|       2                           = Debug Messages|       3                           = Informational Messages|       4                           = All Messages|*/

• 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.');

Hope it will help you.

This mean that your app cannot create application/logs folder, because it doesn't have permission.

Go to applications folder;Create "logs" folder (without quotes);Give permission to folder: chmod 0755 logs.

That's it.