I'm working with archaeological sites, stored as polygons in a MariaDB 10.3 table, and I have PHP 7.2 with GEOS and geoPHP available. I'm creating a page that displays all the related information for a site, and I would like to include nearby sites. The site layer is stored in a Mercator coordinate system (Edit: actually Illinois State Transverse Mercator - [SR-ORG:8669](http://spatialreference.org/ref/sr-org/illinois-state-transverse_mercator/)), with feet as the units, so I think I can use easy distance methods.

I'd like to list any sites within a 1/2 (or maybe 1) mile buffer of the centroid of the current site. I can get the centroid:

```
 SELECT siteid,st_AsWKT(ST_Centroid(aa_allstate_cty.shape)) AS center 
 FROM aa_allstate_cty 
 WHERE siteid = 27200041;

```

And I get back `siteid=27200041` and `center="POINT(3334036.5863035773 4663797.457954536)`

But I don't yet understand how to go the next step of going back and selecting other sites(polygons) which overlap a buffer around that point. What would be the format for the next SQL query?