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Advanced geometry operations in PHP

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README.md

GeoPHP is a open-source native PHP library for doing geometry operations. It is written entirely in PHP and can therefore run on shared hosts. It can read and write a wide variety of formats: WKT (including EWKT), WKB (including EWKB), GeoJSON, KML, GPX, GeoRSS). It works with all Simple-Feature geometries (Point, LineString, Polygon, GeometryCollection etc.) and can be used to get centroids, bounding-boxes, area, and a wide variety of other useful information.

geoPHP also helpfully wraps the GEOS php extension so that applications can get a transparent performance increase when GEOS is installed on the server. When GEOS is installed, geoPHP also becomes fully compliant with the OpenGIS® Implementation Standard for Geographic information. With GEOS you get the full-set of openGIS functions in PHP like Union, IsWithin, Touches etc. This means that applications get a useful "core-set" of geometry operations that work in all environments, and an "extended-set"of operations for environments that have GEOS installed.

See the 'getting started' section below for references and examples of everything that geoPHP can do.

This project is currently looking for co-maintainers. If you think you can help out, please send me a message. Forks are also welcome, please issue pull requests and I will merge them into the main branch.

Getting Started

Example usage

<?php
include_once('geoPHP.inc');

// Polygon WKT example
$polygon = geoPHP::load('POLYGON((1 1,5 1,5 5,1 5,1 1),(2 2,2 3,3 3,3 2,2 2))','wkt');
$area = $polygon->getArea();
$centroid = $polygon->getCentroid();
$centX = $centroid->getX();
$centY = $centroid->getY();

print "This polygon has an area of ".$area." and a centroid with X=".$centX." and Y=".$centY;

// MultiPoint json example
print "<br/>";
$json = 
'{
   "type": "MultiPoint",
   "coordinates": [
       [100.0, 0.0], [101.0, 1.0]
   ]
}';

$multipoint = geoPHP::load($json, 'json');
$multipoint_points = $multipoint->getComponents();
$first_wkt = $multipoint_points[0]->out('wkt');

print "This multipoint has ".$multipoint->numGeometries()." points. The first point has a wkt representation of ".$first_wkt;

More Examples

The Well Known Text (WKT) and Well Known Binary (WKB) support is ideal for integrating with MySQL's or PostGIS's spatial capability. Once you have SELECTed your data with 'AsText('geo_field')' or 'AsBinary('geo_field')', you can put it straight into geoPHP (can be wkt or wkb, but must be the same as how you extracted it from your database):

$geom = geoPHP::load($dbRow,'wkt');

You can collect multiple geometries into one (note that you must use wkt for this):

$geom = geoPHP::load("GEOMETRYCOLLECTION(".$dbString1.",".$dbString2.")",'wkt');

Calling get components returns the sub-geometries within a geometry as an array.

$geom2 = geoPHP::load("GEOMETRYCOLLECTION(LINESTRING(1 1,5 1,5 5,1 5,1 1),LINESTRING(2 2,2 3,3 3,3 2,2 2))");
$geomComponents = $geom2->getComponents();    //an array of the two linestring geometries
$linestring1 = $geomComponents[0]->getComponents(); //an array of the first linestring's point geometries
$linestring2 = $geomComponents[1]->getComponents();
echo $linestring1[0]->x() . ", " . $linestring1[0]->y();    //outputs '1, 1'

An alternative is to use the asArray() method. Using the above geometry collection of two linestrings,

$geometryArray = $geom2->asArray();
echo $geometryArray[0][0][0] . ", " . $geometryArray[0][0][1];    //outputs '1, 1'

Clearly, more complex analysis is possible.

echo $geom2->envelope()->area();

Working with PostGIS

geoPHP, through it's EWKB adapter, has good integration with postGIS. Here's an example of reading and writing postGIS geometries

<?php
include_once('geoPHP.inc');
$host =     'localhost';
$database = 'phayes';
$table =    'test';
$column =   'geom';
$user =     'phayes';
$pass =     'supersecret';

$connection = pg_connect("host=$host dbname=$database user=$user password=$pass");

// Working with PostGIS and Extended-WKB
// ----------------------------

// Using asBinary and GeomFromWKB in PostGIS
$result = pg_fetch_all(pg_query($connection, "SELECT asBinary($column) as geom FROM $table"));
foreach ($result as $item) {
  $wkb = pg_unescape_bytea($item['geom']); // Make sure to unescape the hex blob
  $geom = geoPHP::load($wkb, 'ewkb'); // We now a full geoPHP Geometry object

  // Let's insert it back into the database
  $insert_string = pg_escape_bytea($geom->out('ewkb'));
  pg_query($connection, "INSERT INTO $table ($column) values (GeomFromWKB('$insert_string'))");
}

// Using a direct SELECT and INSERTs in PostGIS without using wrapping functions
$result = pg_fetch_all(pg_query($connection, "SELECT $column as geom FROM $table"));
foreach ($result as $item) {
  $wkb = pack('H*',$item['geom']);   // Unpacking the hex blob
  $geom = geoPHP::load($wkb, 'ewkb'); // We now have a geoPHP Geometry

  // To insert directly into postGIS we need to unpack the WKB
  $unpacked = unpack('H*', $geom->out('ewkb'));
  $insert_string = $unpacked[1];
  pg_query($connection, "INSERT INTO $table ($column) values ('$insert_string')");
}

Credit

Maintainer: Patrick Hayes

Additional Contributors:

This library is open-source and dual-licensed under both the Modified BSD License and GPLv2. Either license may be used at your option.

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