How to query a city based on longitude and latitude in php

As people’s travel needs increase, the importance of geographical location information has become increasingly prominent. In web development, if we need to query city and region information based on latitude and longitude, PHP provides a variety of methods and libraries to achieve this goal.

1. Use PHP built-in functions

PHP has built-in function libraries that can be used to process geographical location information, such as "getgeoip" and "ip2long". These functions can obtain the corresponding longitude and latitude information based on the IP address, and then calculate the city and region where it is located. It should be noted that the results obtained by these functions are for reference only and may contain certain errors.

For example, we can use the following code to obtain the IP address and obtain its corresponding longitude and latitude information:

$ip = $_SERVER['REMOTE_ADDR'];
$details = json_decode(file_get_contents("http://ipinfo.io/{$ip}"));
$lat = $details->loc[0];
$long = $details->loc[1];

Then, we can use other APIs or libraries to achieve more precise city queries.

2. Use third-party API

In addition to PHP built-in functions, we can also use various third-party APIs to query geographical location information. Common ones include Google Maps API, OpenStreetMap API, Baidu Map API and so on. These APIs feature high accuracy, stability and real-time performance, and can meet the needs of most scenarios.

Taking the Baidu Map API as an example, we can obtain the city information corresponding to the longitude and latitude through the following code:

$lat = 40.170799;
$long = 116.370453;
$url="http://api.map.baidu.com/reverse_geocoding/v3/?ak=您的AK&output=json&coordtype=wgs84ll&location=".$lat.",".$long;
$res=file_get_contents($url);
$data=json_decode($res,true);
$city = $data['result']['addressComponent']['city'];

Among them, AK is the API key we applied for on the Baidu Developer Platform, representing us API permissions. In actual use, the AK needs to be replaced with our own API key.

3. Use PHP extension library

In addition to the above two methods, PHP also provides many open source geographical location processing extension libraries, such as Geocoder, Geotools and PhpGeo. These libraries can directly obtain city and regional information corresponding to longitude and latitude by calling the classes and methods they provide, simplifying the query process and code implementation difficulty.

Taking Geocoder as an example, we can use the following code to obtain the city information corresponding to the longitude and latitude:

use Geocoder\Geocoder;
use Geocoder\Query\GeocodeQuery;
use Geocoder\Provider\GoogleMaps\GoogleMaps;
$lat = 40.170799;
$long = 116.370453;
$provider = new GoogleMaps('en', null, 'YOUR_API_KEY');
$geocoder = new Geocoder($provider);
$results = $geocoder->geocodeQuery(GeocodeQuery::create($lat.','.$long));
$city = $results->first()->getLocality();

Among them, YOUR_API_KEY is the API key we applied for in the Google Developers Console, which represents our API permissions . In actual use, YOUR_API_KEY needs to be replaced with our own API key.

Summary

Through the introduction of this article, we have learned about three methods in PHP to query city and regional information based on longitude and latitude: using PHP built-in functions, using third-party APIs and using PHP extension libraries , each method has its advantages and disadvantages, just choose the method that suits your needs. In actual use, special attention needs to be paid to issues such as privacy protection and API authorization to avoid unnecessary security risks and legal risks.

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