Full disclosure, I have no idea what caused this error, but I do know what I did to fix it - just thought I would share, because it was weird.

For background, I was receiving a Slim Error with my Fieldsets, which was remedied by putting every display: value in "". So yay - that was fixed.

But what started happening was when I tried to load my site on the live server (because I pushed zer0 [BL2 anyone?] code until everything was relatively functional in my dev environment), I got an error that read something like,

Fatal error: Cannot access private variable $i in Dipper::$i on line 138 of /[site]/_app/vendor/Statamic/Dipper/Dipper.php

After tweeting the Gentlemen my off-the-handle freakout at the entire site going down, I made sure that in my settings.yaml and settings.default.yaml files both had _yaml_mode set to loose. They were. I made sure 20 times.

So I searched the entire _app folder for "quick" - and I found that yaml was being set to quick in two places:

In _app/core/api/yaml.php, line 21:

public static function getMode() {
     return Config::get('yaml_mode', 'quick');
}

And then in _app/core/statamic.php, line 57:

$yaml_mode       = array_get($preload_config, '_yaml_mode', 'quick');

No matter how many times I checked my config files, the site would not load anything (and again, I have no clue what led to this cropping up, because Statamic is working just fine on every other site, live and dev - so, weird) until I changed quick to loose in both of those sytem files.

I'm not suggesting that anything needs to be done, but I thought I would at least alert y'all to the fact that it had happened and how I "fixed it".

Answered by Fred LeBlanc! Go to answer.