fix collection first() and null-key existence handling

src/Phaseolies/Support/Collection.php

@@ -99,7 +99,7 @@ public function __call($method, $parameters)
      */
     public function __isset($name)
     {
-        return isset($this->data[$name]);
+        return array_key_exists($name, $this->data);
     }
 
     /**
@@ -110,7 +110,7 @@ public function __isset($name)
      */
     public function offsetExists($offset): bool
     {
-        return isset($this->data[$offset]);
+        return array_key_exists($offset, $this->data);
     }
 
     /**
@@ -194,7 +194,11 @@ public function all(): array
      */
     public function first(): mixed
     {
-        return $this->data[0] ?? null;
+        foreach ($this->data as $item) {
+            return $item;
+        }
+
+        return null;
     }
 
     /**

tests/CollectionTest.php

@@ -68,6 +68,17 @@ public function testMagicGetAndIsset()
         $this->assertFalse(isset($collection->baz));
     }
 
+    public function testNullValuesAreStillConsideredPresent()
+    {
+        $collection = new Collection(Model::class, ["foo" => null]);
+
+        $this->assertArrayHasKey("foo", $collection->all());
+        $this->assertTrue(isset($collection["foo"]));
+        $this->assertTrue(isset($collection->foo));
+        $this->assertNull($collection["foo"]);
+        $this->assertNull($collection->foo);
+    }
+
     public function testGetIterator()
     {
         $items = [1, 2, 3];
@@ -97,6 +108,9 @@ public function testFirst()
         $collection = new Collection(Model::class, [1, 2, 3]);
         $this->assertEquals(1, $collection->first());
 
+        $associativeCollection = new Collection(Model::class, ['a' => 10, 'b' => 20]);
+        $this->assertEquals(10, $associativeCollection->first());
+
         $emptyCollection = new Collection(Model::class, []);
         $this->assertNull($emptyCollection->first());
     }