<?php
// $res=isInside($border, $target);

$fn='pages/poligon.data';
$border=json_decode(file_get_contents($fn),true);
// $target=array('lat'=> 41.7103872, 'lng'=> 44.8167936); // tbilisi
// $target=array('lat'=> 42.0196, 'lng'=> 43.1993); // kharagauli
// $target=array('lat'=> 41.9663, 'lng'=> 43.4502); // near 

function getDistance($x1,$y1,$x2,$y2){
	$x=abs($x1-$x2);
	$y=abs($y1-$y2);
	$d=$x*$x+$y*$y;
	$d=sqrt($d);
	return $d;
	}

function isInside($border, $target){
	$degree = 0;
	$border[]=$border[0];
	for ($i=0; $i<count($border) - 1; $i++){
		$a = $border[$i];
		$b = $border[$i + 1];

		# calculate distance of vector
		$A = getDistance($a['lat'], $a['lng'], $b['lat'], $b['lng']);
		$B = getDistance($target['lat'], $target['lng'], $a['lat'], $a['lng']);
		$C = getDistance($target['lat'], $target['lng'], $b['lat'], $b['lng']);
		//echo 'A,B,C=',$A,' ',$B,' ',$C,' = ';
		# calculate direction of vector
		$ta_x = $a['lat'] - $target['lat'];
		$ta_y = $a['lng'] - $target['lng'];
		$tb_x = $b['lat'] - $target['lat'];
		$tb_y = $b['lng'] - $target['lng'];

		$cross = $tb_y * $ta_x - $tb_x * $ta_y;
		$clockwise = (($cross > 0)?1:-1);

		# calculate sum of angles
		$degree = $degree + $clockwise*rad2deg(acos(($B * $B + $C * $C - $A * $A) / (2.0 * $B * $C)));
		//echo $degree.'<br><br>';
		}
	if(abs(round($degree) - 360) <= 3) return 1;
	return 0;
	}

// $res=isInside($border, $target);
?>