Intersections

Intersection Checking

The Intersection helper checks whether two geometries intersect. It supports polygons, polylines, and lines, plus point-in-polygon checks.

Basic usage:

use Location\Coordinate;
use Location\Intersection\Intersection;
use Location\Line;
use Location\Polygon;

$intersection = new Intersection();

$line = new Line(
    new Coordinate(52.237594, 9.287635),
    new Coordinate(52.258154, 11.010313)
);

$polygon = new Polygon();
$polygon->addPoint(new Coordinate(52.56571, 9.998658));
$polygon->addPoint(new Coordinate(52.369576, 9.560167));
$polygon->addPoint(new Coordinate(52.102252, 9.62397));
$polygon->addPoint(new Coordinate(51.983342, 10.132727));
$polygon->addPoint(new Coordinate(52.083498, 10.699142));
$polygon->addPoint(new Coordinate(52.457087, 10.590607));
$polygon->addPoint(new Coordinate(52.56571, 9.998658));

// Fast check: bounds intersection only (may return false positives).
$intersects = $intersection->intersects($line, $polygon, false);

// Precise check: segment intersections + containment.
$intersectsPrecisely = $intersection->intersects($line, $polygon, true);

Point-in-polygon is also supported:

use Location\Coordinate;
use Location\Intersection\Intersection;
use Location\Polygon;

$intersection = new Intersection();
$point = new Coordinate(52.328745, 10.151638);
$intersects = $intersection->intersects($point, $polygon, true);

For point-to-point comparisons, use Coordinate::hasSameLocation() or Coordinate::intersects() instead of Intersection.

The following combinations of geometries can be checked for intersection:

	Point	Line	Polyline	Polygon
Point	yes (same location)	no	no	yes (point inside polygon)
Line	no	yes	yes	yes
Polyline	no	yes	yes	yes
Polygon	yes (point inside polygon)	yes	yes	yes

Precision modes

Intersection::intersects() accepts a third parameter that controls precision:

• false (default) checks only the geometries' bounds. This is fast but can produce false positives when bounds overlap but shapes do not.
• true checks each segment for intersection and also checks polygon containment. This is slower but accurate for supported geometries.

If you pass unsupported combinations (for example, point-to-line), an InvalidGeometryException is thrown.