從 PTX (公共運輸整合資訊流通服務平台) 開放資料產生 geojson 檔

bus-pos.php

<?php
# 範例參數：
# bus-pos.php?city=Taichung&rid=151
# 其他城市名稱請見 http://ptx.transportdata.tw/ptx/Download/API_URI_Convention%E6%96%87%E4%BB%B6_v1.pdf 第 4 頁

parse_str($_SERVER["QUERY_STRING"], $Q);

$time_string = gmdate('D, j M Y H:i:s') . ' GMT';
$signature = base64_encode(hash_hmac("sha1", "x-date: $time_string", $_SERVER['PTX_KEY'], true));

$opts = [
    "http" => [
        "method" => "GET",
        "header" =>
	    'Authorization:hmac username="' . $_SERVER['PTX_ID'] . '", algorithm="hmac-sha1", headers="x-date", signature="' . "$signature\"\n" .
	    "x-date:$time_string\n",
	    "Accept-Encoding: gzip, deflate\n",
    ]
];

$ret = file_get_contents(
    "http://ptx.transportdata.tw/MOTC/v2/Bus/RealTimeByFrequency/City/$Q[city]/$Q[rid]", false, stream_context_create($opts)
);

$ret = array_map( function($v) {
    return [
	"type" => "Feature",
	"properties" => [
	    "name" => $v["PlateNumb"],
	    "Azimuth" => $v["Azimuth"],
	],
	"geometry" => [
	    "type" => "Point",
	    "coordinates" => [
		$v["BusPosition"]["PositionLon"],
		$v["BusPosition"]["PositionLat"],
	    ]
	]
    ];
}, json_decode($ret, true) );

$ret = json_encode([
    "type" => "FeatureCollection",
    "features" => $ret
]);

# firefox 認得 json
# https://developer.mozilla.org/en-US/docs/Tools/JSON_viewer
# 但不認得 geojson
# header('Content-Type: application/vnd.geo+json');
header('Content-Type: application/json');
print $ret;

# 另外 apache2 可能還需要設定 CORS：
# 在 /etc/apache2/sites-available/000-default.conf 裡面加入
# Header set Access-Control-Allow-Origin "*"
# a2enmod headers
# systemctl restart apache2.service


?>