User Comments

people (including the author) have been known to have spent a lot of time 'working' with features that weren't working in the first place.
so read this sentence very, very carefully (taken from above):

"Currently, MySQL does not implement these functions according to the specification. Those that are implemented return the same result as the corresponding MBR-based functions."

"Those that are implemented return the same result as the corresponding MBR-based functions."
The lack of the real implementation to those functions can be for now worked around by passing the result of the query to an appropriate function.
For example, a "within" condition query results with the MBRWithin-function and must then be passed to a "true-Within-function" like those explained by Paul Bourke at http://local.wasp.uwa.edu.au/~pbourke/geometry/.
More specifically:
You have a query:
SELECT AsText(theGeom) AS myPolygon FROM spatialTable WHERE Within(GeomFromText('POINT(463937.596407 4531626.73719)'), theGeom);
You whill loop the MBRWithin-like function result to the specific php function myWithin($row[myPolygon ],"POINT(463937.596407 4531626.73719)") to verify if "really" it is Within.
And here you are:
/******************************************************************************
*
* Purpose: Inside/outside polygon test of a point
* by calculating the number of time an horizontal ray
emanating from a point to the rigth intersects the lines
segments making up the polygon (even=no, odd=yes)
* Author: Paul Bourke, php adaptation: Roger Boily
* return boolean
*
******************************************************************************/
function myWithin($myPolygon,$point) {
$counter = 0;
// get rid of unnecessary stuff
$myPolygon = str_replace("POLYGON","",$myPolygon);
$myPolygon = str_replace("(","",$myPolygon);
$myPolygon = str_replace(")","",$myPolygon);
$point = str_replace("POINT","",$point);
$point = str_replace("(","",$point);
$point = str_replace(")","",$point);
// make an array of points of the polygon
$polygon = explode(",",$myPolygon);
// get the x and y coordinate of the point
$p = explode(" ",$point);
$px = $p[0];
$py = $p[1];
// number of points in the polygon
$n = count($polygon);
$poly1 = $polygon[0];
for ($i=1; $i <= $n; $i++) {
$poly1XY = explode(" ",$poly1);
$poly1x = $poly1XY[0];
$poly1y = $poly1XY[1];
$poly2 = $polygon[$i % $n];
$poly2XY = explode(" ",$poly2);
$poly2x = $poly2XY[0];
$poly2y = $poly2XY[1];
if ($py > min($poly1y,$poly2y)) {
if ($py <= max($poly1y,$poly2y)) {
if ($px <= max($poly1x,$poly2x)) {
if ($poly1y != $poly2y) {
$xinters = ($py-$poly1y)*($poly2x-$poly1x)/($poly2y-$poly1y)+$poly1x;
if ($poly1x == $poly2x || $px <= $xinters) {
$counter++;
}
}
}
}
}
$poly1 = $poly2;
} // end of While each polygon
if ($counter % 2 == 0) {
return(false); // outside
} else {
return(true); // inside
}
}
*******************************
Roger Boily, Gis Consulant [boily at bsw dot org ]
*******************************

Some of the functions mentioned above have now been implemented using non-MBR geometry - take a look at http://forge.mysql.com/wiki/GIS_Functions for more details.

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