PolylineEncoder.php

<?php

class PolylineEncoder
{
    public static function decode(string $value, int $precise = 5): array
    {
        $index = 0;
        $points = [];
        $lat = 0;
        $lng = 0;
        while ($index < strlen($value)) {
            $b = null;
            $shift = 0;
            $result = 0;
            do {
                $b = ord(substr($value, $index++, 1)) - 63;
                $result |= ($b & 0x1f) << $shift;
                $shift += 5;
            } while ($b > 31);
            $dlat = (($result & 1) ? ~($result >> 1) : ($result >> 1));
            $lat += $dlat;
            $shift = 0;
            $result = 0;
            do {
                $b = ord(substr($value, $index++, 1)) - 63;
                $result |= ($b & 0x1f) << $shift;
                $shift += 5;
            } while ($b > 31);
            $dlng = (($result & 1) ? ~($result >> 1) : ($result >> 1));
            $lng += $dlng;
            $points[] = ['x' => $lat / 10 ** $precise, 'y' => $lng / 10 ** $precise];
        }

        return $points;
    }

    public static function encode(array $points, int $precise = 5): string
    {
        $encoder = function ($value) use ($precise) {
            $encoded = '';
            $value = round($value * 10 ** $precise);
            $r = ($value < 0) ? ~($value << 1) : ($value << 1);

            while ($r >= 0x20) {
                $val = (0x20 | ($r & 0x1f)) + 63;
                $encoded .= chr($val);
                $r >>= 5;
            }
            $encoded .= chr($r + 63);

            return $encoded;
        };
        $encoded = '';
        for ($i = 0; $i < count($points); $i++) {
            $x = ($i === 0) ? $points[$i]['x'] : ($points[$i]['x'] - $points[$i - 1]['x']);
            $y = ($i === 0) ? $points[$i]['y'] : ($points[$i]['y'] - $points[$i - 1]['y']);

            $encoded .= $encoder($x).$encoder($y);
        }

        return $encoded;
    }
}