title: CodeIgniter's error log doesn't seem to report all errors
body: <p>I'm currently creating a web application through linux OS (debian), using php7, codeIgniter 3, Nginx and Mysql.</p>
  
  <p>Few months ago, all my PHP errors used to be reported in the default nginx log error (located at : /var/log/nginx/)</p>
  
  <p>But recently, I have configured CodeIgniter in purpose to report those errors inside the folder of my application.</p>
  
  <p>It seemed to work, because I noticed that my current errors were repported in this new log file.
  However, "some" errors don't seem to be reported. For example, I have a form in my web application, running aswell with Javascript (ajax use). Once I send the form, I can notice in my browser's console an Error 500 (internal server error). However, this error is not reported in my error log file ! (and I already checked in the former log file belonging to Nginx, there's nothing too)</p>
  
  <p>What am I supposed to do ?</p>
  
  <p>Thanks you.</p>