<?php

/**
 * @name 围栏算法，判断一个坐标，是否在围栏里面.如：['113.664673,34.810146','113.681667,34.796896','113.69231,34.794711','113.702009,34.809159']
 * @author macnie <[email protected]>
 * @param array $fences 围栏，是一组坐标数组 如：113.674458,34.804719
 * @param string $point 要判断的坐标
 * @return bool
 */
function in_fences($fences, $point) {
    $nvert = count($fences);
    $vertx = [];
    $verty = [];
    list($testy, $testx) = explode(',', $point);
    foreach ($fences as $r) {
        list($lng, $lat) = explode(',', $r);
        $vertx[] = $lat;
        $verty[] = $lng;
    }
    $i = $j = $c = 0;
    for ($i = 0, $j = $nvert - 1; $i < $nvert; $j = $i++) {
        if (( ($verty[$i] > $testy) != ($verty[$j] > $testy) ) &&
            ($testx < ($vertx[$j] - $vertx[$i]) * ($testy - $verty[$i]) / ($verty[$j] - $verty[$i]) + $vertx[$i]))
            $c = !$c;
    }
    return $c;
}

//围栏map数据
$fences=[
'113.626809,34.75027',
    '113.630975,34.752162',
    '113.626102,34.753941'
];
$p="113.633093,34.751396"; //当前的位置
$res = in_fences($fences,$p);
var_dump($res);