Pretty much a complete rewrite, but it's only one class so I won't assume you're very impressed

Author: marcusirgens

RandomFactor.php

@@ -1,9 +1,13 @@
 <?php
 
-require_once(__DIR__.'/src/Core.php');
-
 if (!function_exists('random_factor')) {
-	function random_factor($lang = 'en', $spacing = ' ', $adjectives = 1, $nouns = 1) {
-		return RandomFactor\Core::generate($lang, $spacing, $adjectives, $nouns);
-	}
-}
+    function random_factor($lang = 'en', $spacing = ' ', $adjectives = 1, $nouns = 1)
+    {
+        return marcuspi\RandomFactor\Words::create()
+            ->language($lang)
+            ->spacing($spacing)
+            ->adjectives($adjectives)
+            ->nouns($nouns)
+            ->generate();
+    }
+}

composer.json

@@ -19,6 +19,9 @@
         "issues": "https:\/\/github.com\/marcusirgens\/RandomFactor\/issues"
     },
     "autoload": {
+        "psr-4": {
+            "marcuspi\\RandomFactor\\": "src/marcuspi/RandomFactor/"
+        },
         "files": [
             "RandomFactor.php"
         ]

src/Core.php

@@ -0,0 +1,160 @@
+<?php
+declare(strict_types=1);
+
+namespace marcuspi\RandomFactor;
+
+class Words
+{
+    private static $languages = [
+        'no' => 'no-nb',
+        'en' => 'en'
+    ];
+    
+    private $language;
+    private $spacing;
+    private $nouns;
+    private $adjectives;
+    
+    /**
+     * Creates new Words.
+     *
+     * @access public
+     * @param string $language The language to use (default: "en")
+     * @param string $spacing Character(s) to used to split the words (default: " ")
+     * @param int $nouns Number of nouns (default: 1)
+     * @param int $adjectives Number of adjectives (default: 1)
+     */
+    public function __construct($language = "en", $spacing = " ", $nouns = 1, $adjectives = 1)
+    {
+        $this->language($language);
+        $this->spacing($spacing);
+        $this->nouns($nouns);
+        $this->adjectives($adjectives);
+    }
+    
+    /**
+     * Sets which language that should be used
+     *
+     * @access public
+     * @param string $language One of "no", "en".
+     * @return self
+     */
+    public function language(string $language): Words
+    {
+        if (!array_key_exists(mb_strtolower($language), static::$languages)) {
+            throw new \Exception('Language \'' . $language . '\' not found');
+        }
+        
+        $this->language = mb_strtolower($language);
+        
+        return $this;
+    }
+    
+    /**
+     * Sets the character(s) to used to split the words
+     *
+     * @access public
+     * @param string $spacing
+     * @return self
+     */
+    public function spacing(string $spacing): Words
+    {
+        $this->spacing = $spacing;
+        
+        return $this;
+    }
+    
+    /**
+     * Sets the number of nouns
+     *
+     * @access public
+     * @param int $nouns A positive integer
+     * @return self
+     */
+    public function nouns(int $nouns): Words
+    {
+        if ($nouns < 0) {
+            throw new \Exception('Number of nouns must be a positive integer');
+        }
+        
+        $this->nouns = $nouns;
+        
+        return $this;
+    }
+    
+    /**
+     * Sets the number of adjectives
+     *
+     * @access public
+     * @param int $adjectives A positive integer
+     * @return self
+     */
+    public function adjectives(int $adjectives): Words
+    {
+        if ($adjectives < 0) {
+            throw new \Exception('Number of adjectives must be a positive integer');
+        }
+        
+        $this->adjectives = $adjectives;
+        
+        return $this;
+    }
+    
+    /**
+     * Static creation.
+     *
+     * @access public
+     * @static
+     * @return self
+     */
+    public static function create()
+    {
+        return new static;
+    }
+    
+    /**
+     * Generates the random words.
+     *
+     * @access public
+     * @return string
+     */
+    public function generate(): string
+    {
+        
+        $wordlist = $this->readWordList();
+        
+        $words = [];
+        
+        for ($i = 0; $i < $this->adjectives; $i++) {
+            $words[] = $wordlist['adjectives'][random_int(0, count($wordlist['adjectives']) - 1)];
+        }
+        
+        for ($i = 0; $i < $this->nouns; $i++) {
+            $words[] = $wordlist['nouns'][random_int(0, count($wordlist['nouns']) - 1)];
+        }
+        
+        return implode($this->spacing, $words);
+    }
+    
+    /**
+     * Alias for self::generate()
+     *
+     * @access public
+     * @return string
+     */
+    public function __toString(): string
+    {
+        return $this->generate();
+    }
+    
+    private function readWordList(): array
+    {
+        $wordfile = __DIR__ . '/lang/' . static::$languages[$this->language] . '.json';
+        
+        if (!file_exists($wordfile)) {
+            throw new \Exception('Language file \'' . $wordfile . '\' not found');
+        }
+        
+        return json_decode(file_get_contents($wordfile), true);
+    }
+}