# phpgeo - A Simple Geo Library for PHP

phpgeo provides abstractions to geographical coordinates (including support for different ellipsoids) and allows you to calculate geographical distances between coordinates with high precision.

<!-- MarkdownTOC autolink=true bracket=round depth=0 autoanchor=false -->

- [phpgeo - A Simple Geo Library for PHP](#phpgeo---a-simple-geo-library-for-php)
  - [Requirements](#requirements)
  - [Documentation](#documentation)
  - [Installation](#installation)
  - [License](#license)
  - [Features](#features)
  - [Examples/Usage](#examplesusage)
    - [Distance between two coordinates (Vincenty's Formula)](#distance-between-two-coordinates-vincentys-formula)
    - [Simplifying a polyline](#simplifying-a-polyline)
    - [Polygon contains a point (e.g. "GPS geofence")](#polygon-contains-a-point-eg-%22gps-geofence%22)
    - [Formatted output of coordinates](#formatted-output-of-coordinates)
      - [Decimal Degrees](#decimal-degrees)
      - [Degrees/Minutes/Seconds (DMS)](#degreesminutesseconds-dms)
      - [GeoJSON](#geojson)
  - [Development](#development)
    - [Run Tests](#run-tests)
  - [Miscellaneous](#miscellaneous)
  - [Credits](#credits)

<!-- /MarkdownTOC -->

## Requirements

Minimum required PHP version is 7.0.

## Documentation

The documentation is available at https://phpgeo.marcusjaschen.de/

API documentation is available as well: https://phpgeo.marcusjaschen.de/api/

## Installation

Using [Composer](https://getcomposer.org), just add it to your `composer.json` by running:

```
composer require mjaschen/phpgeo
```

## License

Starting with version 2.0.0 phpgeo is licensed under the MIT license. Older versions were GPL-licensed.

## Features

**Info:** Please visit the **[documentation site](https://phpgeo.marcusjaschen.de/)** for complete and up-to-date documentation with many examples!

phpgeo provides the following features (follow the links for examples):

- abstractions of several geometry objects ([coordinate/point](https://phpgeo.marcusjaschen.de/Geometries/Coordinate.html),
  [line](https://phpgeo.marcusjaschen.de/Geometries/Line.html),
  [polyline/GPS track](https://phpgeo.marcusjaschen.de/Geometries/Polyline.html),
  [polygon](https://phpgeo.marcusjaschen.de/Geometries/Polygon.html)
- support for different [ellipsoids](https://phpgeo.marcusjaschen.de/Geometries/Ellipsoid.html), e.g. WGS-84
- [length/distance/perimeter calculations](https://phpgeo.marcusjaschen.de/Calculations/Distance_and_Length.html)
  with different implementations (Haversine, Vincenty)
- [Geofence](https://phpgeo.marcusjaschen.de/Calculations/Geofence.html) calculation,
  i. e. answering the question "Is this point contained in that area/polygon?"
- [formatting and output](https://phpgeo.marcusjaschen.de/Formatting_and_Output/index.html) of geometry objects
  (GeoJSON, nice strings, e. g. `18° 54′ 41″ -155° 40′ 42″`)
- calculation of [bearing angle between two points](https://phpgeo.marcusjaschen.de/Calculations/Bearing_and_Destination.html#page_Bearing-between-two-points)
  (spherical or with Vincenty's formula)
- calculation of a [destination point for a given starting point](https://phpgeo.marcusjaschen.de/Calculations/Bearing_and_Destination.html#page_Destination-point-for-given-bearing-and-distance),
  bearing angle, and distance (spherical or with Vincenty's formula)
- calculation of the [perpendicular distance between a point and a line](https://phpgeo.marcusjaschen.de/Calculations/Perpendicular_Distance.html)
- getting segments of a [polyline](https://phpgeo.marcusjaschen.de/Geometries/Polyline.html#page_Segments)
  /[polygon](https://phpgeo.marcusjaschen.de/Geometries/Polygon.html#page_Segments),
- [reversing direction](https://phpgeo.marcusjaschen.de/Geometries/Polygon.html#page_Reverse-Direction)
  of polyline/polygon

## Examples/Usage

This list is incomplete, please visit the [documentation site](https://phpgeo.marcusjaschen.de/)
for the full monty of documentation and examples!

### Distance between two coordinates (Vincenty's Formula)

Use the calculator object directly:

```php
<?php

use Location\Coordinate;
use Location\Distance\Vincenty;

$coordinate1 = new Coordinate(19.820664, -155.468066); // Mauna Kea Summit
$coordinate2 = new Coordinate(20.709722, -156.253333); // Haleakala Summit

$calculator = new Vincenty();

echo $calculator->getDistance($coordinate1, $coordinate2); // returns 128130.850 (meters; ≈128 kilometers)
```

or call the `getDistance()` method of a Coordinate object by injecting a calculator object:

```php
<?php

use Location\Coordinate;
use Location\Distance\Vincenty;

$coordinate1 = new Coordinate(19.820664, -155.468066); // Mauna Kea Summit
$coordinate2 = new Coordinate(20.709722, -156.253333); // Haleakala Summit

echo $coordinate1->getDistance($coordinate2, new Vincenty()); // returns 128130.850 (meters; ≈128 kilometers)
```

### Simplifying a polyline

Polylines can be simplified to save storage space or bandwidth. Simplification is done with the [Ramer–Douglas–Peucker algorithm](https://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm) (AKA Douglas-Peucker algorithm).

```php
<?php

use Location\Coordinate;
use Location\Polyline;
use Location\Distance\Vincenty;

$polyline = new Polyline();
$polyline->addPoint(new Coordinate(10.0, 10.0));
$polyline->addPoint(new Coordinate(20.0, 20.0));
$polyline->addPoint(new Coordinate(30.0, 10.0));

$processor = new Simplify($polyline);

// remove all points which perpendicular distance is less
// than 1500 km from the surrounding points.
$simplified = $processor->simplify(1500000);

// simplified is the polyline without the second point (which
// perpendicular distance is ~1046 km and therefore below
// the simplification threshold)
```

### Polygon contains a point (e.g. "GPS geofence")

phpgeo has a polygon implementation which can be used to determinate if a point is contained in it or not.
A polygon consists of at least three points. Points are instances of the `Coordinate` class.

**Warning:** The calculation gives wrong results if the polygons has points on both sides of the 180/-180 degrees meridian.

```php
<?php

use Location\Coordinate;
use Location\Polygon;

$geofence = new Polygon();

$geofence->addPoint(new Coordinate(-12.085870,-77.016261));
$geofence->addPoint(new Coordinate(-12.086373,-77.033813));
$geofence->addPoint(new Coordinate(-12.102823,-77.030938));
$geofence->addPoint(new Coordinate(-12.098669,-77.006476));

$outsidePoint = new Coordinate(-12.075452, -76.985079);
$insidePoint = new Coordinate(-12.092542, -77.021540);

var_dump($geofence->contains($outsidePoint)); // returns bool(false) the point is outside the polygon
var_dump($geofence->contains($insidePoint)); // returns bool(true) the point is inside the polygon
```

### Formatted output of coordinates

You can format a coordinate in different styles.

#### Decimal Degrees

```php
<?php

use Location\Coordinate;
use Location\Formatter\Coordinate\DecimalDegrees;

$coordinate = new Coordinate(19.820664, -155.468066); // Mauna Kea Summit

echo $coordinate->format(new DecimalDegrees());
```

#### Degrees/Minutes/Seconds (DMS)

```php
<?php

use Location\Coordinate;
use Location\Formatter\Coordinate\DMS;

$coordinate = new Coordinate(18.911306, -155.678268); // South Point, HI, USA

$formatter = new DMS();

echo $coordinate->format($formatter); // 18° 54′ 41″ -155° 40′ 42″

$formatter->setSeparator(", ")
    ->useCardinalLetters(true)
    ->setUnits(DMS::UNITS_ASCII);

echo $coordinate->format($formatter); // 18° 54' 41" N, 155° 40' 42" W
```

#### GeoJSON

```php
<?php

use Location\Coordinate;
use Location\Formatter\Coordinate\GeoJSON;

$coordinate = new Coordinate(18.911306, -155.678268); // South Point, HI, USA

echo $coordinate->format(new GeoJSON()); // { "type" : "point" , "coordinates" : [ -155.678268, 18.911306 ] }
```

## Development

### Run Tests

Before submitting a pull request, please be sure to run all checks and tests and ensure everything is green.

To run the checks and tests, it's the easiest to use the provided Composer scripts:

- install development tools with [Phive](https://phar.io/): `phive install`
- lint PHP files for syntax errors: `composer ci:lint`
- run static analysis with [Psalm][] and report errors: `composer ci:psalm`
- run unit tests with PHPUnit: `composer ci:tests`

To run all checks and tests at once, just use `composer ci`.

Of course, it's possible to use the test runners directly, e. g. for PHPUnit:

```shell
./tools/phpunit
```

Psalm:

```shell
./vendor/bin/psalm
```

## Miscellaneous

[@clemdesign](https://github.com/clemdesign) created a [TypeScript port](https://github.com/clemdesign/typescript-tsgeo) of phpgeo.

## Credits

* Marcus Jaschen <mail@marcusjaschen.de>
* [Chris Veness](http://www.movable-type.co.uk/scripts/latlong-vincenty.html) - JavaScript implementation of the [Vincenty formula](http://en.wikipedia.org/wiki/Vincenty%27s_formulae) for distance calculation
* Ersts,P.J., Horning, N., and M. Polin[Internet] Perpendicular Distance Calculator(version 1.2.2) [Documentation](http://biodiversityinformatics.amnh.org/open_source/pdc/documentation.php). American Museum of Natural History, Center for Biodiversity and Conservation. Available from http://biodiversityinformatics.amnh.org/open_source/pdc. Accessed on 2013-07-07.
* W. Randolph Franklin, PNPOLY - Point Inclusion in Polygon Test [Documentation](http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html)
* [Richard Barnes](https://github.com/r-barnes) Polyline GeoJSON Formatter
* [Paul Vidal](https://github.com/paulvl) Polygon Implementation

[Psalm]: https://github.com/vimeo/psalm