Packages in PHP

src_Acme_Animal_Cat.php

<?php
namespace Acme:Animal;

class Cat {
  public function __construct() {
    echo 'Created ' . self::class . ' from package ' . __PACKAGE__;
  }
}

src_Acme_package.php

<?php
// package declaration
package Acme declare(strict_types=1);

// future extensions of package
package Acme declare(strict_types=1) {
  const VERSION = '1.0';
  function createCat() : Animal\Cat {}
}

src_Acme_Plant.php

<?php
namespace Acme:;

class Plant {} // class directly under package namespace

src_all-in-one.php

<?php
package Acme declare(strict_types=1) {
  const VERSION = '1.0';
  function createCat() : Animal\Cat {}
  
  class Plant {}
  
  namespace Animal {
    class Cat {}
  }
}

package AnotherPackage {
  class A {} // here strict_types is default which is 0
}

usage.php

<?php

use Acme:Animal\Cat;
use Acme:Plant;
use const Acme:VERSION;
use function Acme:createCat;

$cat = new Cat(); // autoload detects package name "Acme" and loads it for eg. from "src/Acme/package.php" or whatever
// it also echoes "Created Acme:Animal\Cat from package Acme"

echo Cat::class; // Acme:Animal\Cat;

$plant = new Plant(); // autoload detects package name "Acme" but it's already been loaded, then do nothing

$anotherCat = createCat(); // same as above

$version = VERSION; // same as above