php附近的商家实现方法—geohash算法实现

张绪航 2019-12-14 10:52:03 2721 浏览 php PHP

示例：根据用户自身定位经纬度：39.98123848, 116.30683690，然后查找附近的商家

<?php
require_once('geohash.class.php');
$geohash = new Geohash;
//得到这点的hash值
$hash = $geohash->encode(39.98123848, 116.30683690);
//取前缀，前缀约长范围越小
$prefix = substr($hash, 0, 6);
//取出相邻八个区域
$neighbors = $geohash->neighbors($prefix);
array_push($neighbors, $prefix);
print_r($neighbors);
?>

得到9个geohash值：

Array(
    [top] => wx4eqx
    [bottom] => wx4eqt
    [right] => wx4eqy
    [left] => wx4eqq
    [topleft] => wx4eqr
    [topright] => wx4eqz
    [bottomright] => wx4eqv
    [bottomleft] => wx4eqm
    [0] => wx4eqw
)

范围如下图：

用sql语句查询：

SELECT * FROM table_name WHERE geohash LIKE 'wx4eqw%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqx%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqt%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqy%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqq%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqr%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqz%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqv%';
SELECT * FROM table_name WHERE geohash LIKE 'wx4eqm%';

geohash.class.php代码如下：

<?php
/**
 * Geohash generation class for php
 * encode and decode geohashes
 * Find neighbors
 */
namespace libs;
class Geohash {
	private $bitss = array(16, 8, 4, 2, 1);
	private $neighbors = array();
	private $borders = array();

	private $coding = "0123456789bcdefghjkmnpqrstuvwxyz";
	private $codingMap = array();

	public function Geohash() {
		$this->neighbors['right']['even'] = 'bc01fg45238967deuvhjyznpkmstqrwx';
		$this->neighbors['left']['even'] = '238967debc01fg45kmstqrwxuvhjyznp';
		$this->neighbors['top']['even'] = 'p0r21436x8zb9dcf5h7kjnmqesgutwvy';
		$this->neighbors['bottom']['even'] = '14365h7k9dcfesgujnmqp0r2twvyx8zb';

		$this->borders['right']['even'] = 'bcfguvyz';
		$this->borders['left']['even'] = '0145hjnp';
		$this->borders['top']['even'] = 'prxz';
		$this->borders['bottom']['even'] = '028b';

		$this->neighbors['bottom']['odd'] = $this->neighbors['left']['even'];
		$this->neighbors['top']['odd'] = $this->neighbors['right']['even'];
		$this->neighbors['left']['odd'] = $this->neighbors['bottom']['even'];
		$this->neighbors['right']['odd'] = $this->neighbors['top']['even'];

		$this->borders['bottom']['odd'] = $this->borders['left']['even'];
		$this->borders['top']['odd'] = $this->borders['right']['even'];
		$this->borders['left']['odd'] = $this->borders['bottom']['even'];
		$this->borders['right']['odd'] = $this->borders['top']['even'];

		//build map from encoding char to 0 padded bitfield
		for($i=0; $i<32; $i++) {
			$this->codingMap[substr($this->coding, $i, 1)] = str_pad(decbin($i), 5, "0", STR_PAD_LEFT);
		}
	}
	/*经纬度解码*/
	public function decode($hash) {
		//解码成二进制
		$binary = "";
		$hl = strlen($hash);
		for ($i=0; $i<$hl; $i++) {
			$binary .= $this->codingMap[substr($hash, $i, 1)];
		}
		//将二进制分为经纬度
		$bl = strlen($binary);
		$blat = "";
		$blong = "";
		for ($i=0; $i<$bl; $i++) {
			if ($i%2)
				$blat=$blat.substr($binary, $i, 1);
			else
				$blong=$blong.substr($binary, $i, 1);
		}

		//now concert to decimal
		$lat = $this->binDecode($blat, -90, 90);
		$long = $this->binDecode($blong, -180, 180);

		//figure out how precise the bit count makes this calculation
		$latErr = $this->calcError(strlen($blat), -90, 90);
		$longErr = $this->calcError(strlen($blong), -180, 180);

		//how many decimal places should we use? There's a little art to
		//this to ensure I get the same roundings as geohash.org
		$latPlaces = max(1, -round(log10($latErr))) - 1;
		$longPlaces = max(1, -round(log10($longErr))) - 1;

		//round it
		$lat = round($lat, $latPlaces);
		$long = round($long, $longPlaces);
		return array($lat, $long);
	}

	private function calculateAdjacent($srcHash, $dir) {
		$srcHash = strtolower($srcHash);
		$lastChr = $srcHash[strlen($srcHash) - 1];
		$type = (strlen($srcHash) % 2) ? 'odd' : 'even';
		$base = substr($srcHash, 0, strlen($srcHash) - 1);
		if (strpos($this->borders[$dir][$type], $lastChr) !== false) {
			$base = $this->calculateAdjacent($base, $dir);
		}
		return $base . $this->coding[strpos($this->neighbors[$dir][$type], $lastChr)];
	}

	public function neighbors($srcHash) {
		$geohashPrefix = substr($srcHash, 0, strlen($srcHash) - 1);
	 	$neighbors['top'] = $this->calculateAdjacent($srcHash, 'top');
	 	$neighbors['bottom'] = $this->calculateAdjacent($srcHash, 'bottom');
	 	$neighbors['right'] = $this->calculateAdjacent($srcHash, 'right');
	 	$neighbors['left'] = $this->calculateAdjacent($srcHash, 'left');
	 	$neighbors['topleft'] = $this->calculateAdjacent($neighbors['left'], 'top');
	 	$neighbors['topright'] = $this->calculateAdjacent($neighbors['right'], 'top');
	 	$neighbors['bottomright'] = $this->calculateAdjacent($neighbors['right'], 'bottom');
	 	$neighbors['bottomleft'] = $this->calculateAdjacent($neighbors['left'], 'bottom');
		return $neighbors;
	}
	/*经纬度编码*/
	public function encode($lat, $long) {
		//how many bits does latitude need?
		$plat = $this->precision($lat);
		$latbits = 1;
		$err = 45;
		while($err > $plat) {
			$latbits++;
			$err /= 2;
		}
		//how many bits does longitude need?
		$plong = $this->precision($long);
		$longbits = 1;
		$err = 90;
		while($err > $plong) {
			$longbits++;
			$err /= 2;
		}
		//bit counts need to be equal
		$bits = max($latbits, $longbits);
		//as the hash create bits in groups of 5, lets not
		//waste any bits - lets bulk it up to a multiple of 5
		//and favour the longitude for any odd bits
		$longbits = $bits;
		$latbits = $bits;
		$addlong = 1;
		while (($longbits + $latbits) % 5 != 0) {
			$longbits += $addlong;
			$latbits += !$addlong;
			$addlong = !$addlong;
		}
		//encode each as binary string
		$blat = $this->binEncode($lat, -90, 90, $latbits);
		$blong = $this->binEncode($long, -180, 180, $longbits);
		//merge lat and long together
		$binary = "";
		$uselong = 1;
		while (strlen($blat) + strlen($blong)) {
			if ($uselong) {
				$binary = $binary.substr($blong, 0, 1);
				$blong = substr($blong, 1);
			} else {
				$binary = $binary.substr($blat, 0, 1);
				$blat = substr($blat, 1);
			}
			$uselong = !$uselong;
		}
		//convert binary string to hash
		$hash = "";
		for ($i=0; $i<strlen($binary); $i+=5) {
			$n = bindec(substr($binary, $i, 5));
			$hash = $hash.$this->coding[$n];
		}
		return $hash;
	}
	/**
	* What's the maximum error for $bits bits covering a range $min to $max
	*/
	private function calcError($bits, $min, $max) {
		$err = ($max - $min) / 2;
		while ($bits--)
			$err /= 2;
		return $err;
	}

	/*
	* returns precision of number
	* precision of 42 is 0.5
	* precision of 42.4 is 0.05
	* precision of 42.41 is 0.005 etc
	*/
	private function precision($number) {
		$precision = 0;
		$pt = strpos($number,'.');
		if ($pt !== false) {
			$precision = -(strlen($number) - $pt - 1);
		}
		return pow(10, $precision) / 2;
	}
	/**
	* create binary encoding of number as detailed in http://en.wikipedia.org/wiki/Geohash#Example
	* removing the tail recursion is left an exercise for the reader
	*/
	private function binEncode($number, $min, $max, $bitcount) {
		if ($bitcount == 0)
			return "";
		#echo "$bitcount: $min $max<br>";
		//this is our mid point - we will produce a bit to say
		//whether $number is above or below this mid point
		$mid = ($min + $max) / 2;
		if ($number > $mid)
			return "1" . $this->binEncode($number, $mid, $max, $bitcount - 1);
		else
			return "0" . $this->binEncode($number, $min, $mid, $bitcount - 1);
	}

	/**
	* decodes binary encoding of number as detailed in http://en.wikipedia.org/wiki/Geohash#Example
	* removing the tail recursion is left an exercise for the reader
	*/
	private function binDecode($binary, $min, $max) {
		$mid = ($min + $max) / 2;
		if (strlen($binary) == 0)
			return $mid;
		$bit = substr($binary, 0, 1);
		$binary = substr($binary, 1);
		if ($bit == 1)
			return $this->binDecode($binary, $mid, $max);
		else
			return $this->binDecode($binary, $min, $mid);
	}
}