nginx chops off error messages from PHP+xdebug?

I currently have some nightmares with PHP 5.6 (application is a #CodeIgniter2 application and cannot run on newer versions, I guess upgrading CI2 to CI3 + PHP to 7.x will make it more messier than before).

Here is what I get from an AJAX request:
<div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;">

<h4>A PHP Error was encountered</h4>

<p>Severity: Warning</p>

Also no error is being logged but I enabled it in FPM's php.ini file.
#CodeIgniter2 nginx php-fpm php56 xdebug
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