PHP / Mongo geoJSON Loop is not valid

It is because your coordinates are identical that creates an anomaly in the polygon shape: [-97.1788790, 49.9193990] and [-97.2035980, 49.9193990]. In your code remove or change any of the duplicate coordinate,

"coordinates": [[    [-97.209091, 49.905691],    [-97.206345, 49.918072],    [-97.178879, 49.919399], // this line    [-97.165146, 49.907903],    [-97.164459, 49.892865],    [-97.180939, 49.889326],    [-97.197418, 49.895077],    [-97.200165, 49.902596],    [-97.203598, 49.919399], // and this one    [-97.216644, 49.928682],    [-97.244797, 49.927356],    [-97.255096, 49.913209],    [-97.209091, 49.905691]]]

As I mentioned in comments the better tool to query spatial data would be to use PostGIS.

For example PostGIS have the ST_validReason() to find the problem with polygon and a st_makevalid to fix but if this is not an option then I would create a service available to your PHP script with shapely python library https://github.com/Toblerity/Shapely

http://toblerity.org/shapely/manual.html

The first premise of Shapely is that Python programmers should be able to perform PostGIS type geometry operations outside of an RDBMS

Certainly shapely is a popular tool, and you should get future help with in on StackOverflow or gis.stackexchange.com from more experienced users

I think the problem you are trying to solve is not as trivial as it sounds.

So I would perform following steps:

1 Find how to do it with shapely

similar questions: Splitting self-intersecting polygon only returned one polygon in shapely in Python

2 create a simple php service which will pass query details to python script

3 Shapely will not prevent the creation of invalid polygon, but exceptions will be raised when they are operated on. So basically on such exception, I would call the script from step 1.

If this is just for one of query, I would just use QGIS software ( import points as CSV, create a new shapefile layer ( of type polygon ), and use Numerical vertex edit plugin )

update

I think the polygon should be fixed by the tool that created it so in this case, it should be a user. Maybe you fix that problem by looking from a different angle and if the shape is coming from the user and is drawn in GoogleMap in your app maybe enforce no intersection during drawing.

Found also this Drawing a Polygon ( sorting points and creating polygon with no intersection )