named-constructors to the rescue

geolocation-basic.php

<?php

declare(strict_types=1);

namespace Example;

final class Geolocation
{
    private float $latitude;
    
    private float $longitude;
    
    public function __construct(float $latitude, float $longitude)
    {
        $this->latitude = $latitude;
        $this->longitude = $longitude;
    }

    public function latitude(): float 
    {
        return $this->latitude;
    }

    public function longitude(): float 
    {
        return $this->latitude;
    }
}

geolocation-dx.php

<?php

$latitude = Geolocation::fromDMM("40° 26.767′ N 79° 58.933′ W")->latitude();
$geoloc2 = Geolocation::fromCoordinates(38.1256, -25.1235);

geolocation-final.php

<?php

declare(strict_types=1);
 
namespace Example;
 
use InvalidArgumentException;

final class Geolocation
{
    private const REGEXP_DDM = 'a-regexp-to-parse-a-ddm-string';

    private float $latitude;
    
    private float $longitude;

    public static function fromDDM(string $coordinates): self 
    {
        if (!preg_match(self::REGEXP_DDM, $coordinates, $match)) {
            throw new InvalidArgumentException('The coordinate are invalid');
        }
    
        //obviously this part will be more complicated...
        $latitude  = $match[1];
        $longitude = $match[2];
        
        return self::fromCoordinates($latitude, $longitude);
    }

    public static function fromCoordinates($latitude, $longitude): self 
    {
          //$latitude and $longitude filtering happens here

          return new self($latitude, $longitude);
    }

    private function __construct(float $latitude, float $longitude)
    {
        $this->latitude = $latitude;
        $this->longitude = $longitude;
    }

    public function latitude(): float 
    {
        return $this->latitude;
    }

    public function longitude(): float 
    {
        return $this->latitude;
    }
}

geolocation-from-ddm.php

<?php

declare(strict_types=1);
 
namespace Example;
 
use InvalidArgumentException;

final class Geolocation
{
    private const REGEXP_DDM = 'a-regexp-to-parse-a-ddm-string';

    public static function fromDDM(string $coordinates): self 
    {
        if (!preg_match(self::REGEXP_DDM, $coordinates, $match)) {
            throw new InvalidArgumentException('The coordinate do not represent a valid DDM string');
        }
    
        //obviously this part will be more complicated...
        $latitude  = $match[1];
        $longitude = $match[2];
        
        return new self($latitude, $longitude);
    }

    //... rest of the code stay unchanged
}

geolocation-validation.php

<?php

declare(strict_types=1);
 
namespace Example;
 
final class Geolocation
{
     private float $latitude;
     
     private float $longitude;
     
     public function __construct(float $latitude, float $longitude)
     {
         $this->latitude = $this->filterLatitude($latitude);
         $this->longitude = $this->filterLongitude($longitude);
     }
 
    private function filterLatitude(float $latitude): float 
    {
       //filtering logic
       return $latitude;
    }
 
    private function filterLongitude(float $longitude): float 
    {
       //filtering logic
       return $longitude;
    }
    //... rest of the code stay unchanged
}

more-named-constructor.php

<?php

$geoloc1 = Geolocation::fromTenTen("MED 8FV N9K5");
$geoloc2 = Geolocation::fromGeoHash("u1513y");

named-constructor-too-generic.php

<?php
 
$geoloc1 = Geolocation::make("MED 8FV N9K5");
$geoloc2 = Geolocation::make("u1513y");

narrow-variable.php

<?php
$content = (string) $request->getBody();
$geoloc = Geolocation::fromJsonCoordinates($content);
//and the Json String should be clearly specify at the name constructor definition site.
// string should be "[5.142358,-4.12458]"

variable-too-broad.php

<?php
$geoloc = Geolocation::fromRequest($request);
//where $request is a Psr\Http\Message\RequestInterface;