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phparraysvariadic

Using object implementing ArrayAccess and Iterator as variadic parameter

I have a class that implements both ArrayAccess and Iterator.

I'm trying to figure out how to pass this object variadic parameter to a native function like array_merge:

array_merge(...$object);

To my disappointment I'm getting an error saying that $object is not an array.

array_merge(): Argument #1 is not an array

I've looked at these other interfaces but non of them seem obvious: IteratorAggregate, Serializable, Countable. Also ArrayObject turned out to be a dead end.

I do have a getter for to convert to array. But I was kind of hopping to discover my $object transform into an array just by implementing either ArrayAccess or Iterator, since it is about unfolding the array.

Is there another interface I can implement to make my class be more array-like?

Solution

  • This is a new language feature as documented in the migration guide from 5.5.x to 5.6.x in the manual (section Argument unpacking via ...), you must be on a pre-5.6.x runtime.

    If you cannot upgrade your runtime, you must make use of your getter for converting it to an array (similar to ArrayObject's getArrayCopy):

    call_user_func_array('array_merge', $arr->getArrayCopy());

    Tests

    The code below (based on PHP's documentation examples for ArrayAccess and Iterator) executed successfully on PHP 5.6.2, 5.6.17 and 7.0.1. It fails indeed on older versions (5.5.31 and older).

    $arr = new MyArray();
$arr[0] = array(1, 2);
$arr[1] = array(3, 4);

// MyArray
print(get_class($arr));

// Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 ) 
print_r(array_merge(...$arr));

    Implementation of MyArray:

    class MyArray implements ArrayAccess, Iterator
{
      private $container = array();
      private $position = 0;

      public function getArrayCopy() {
        return $this->container;
      }

      public function offsetSet($offset, $value) {
        if (is_null($offset)) {
            $this->container[] = $value;
        } else {
            $this->container[$offset] = $value;
        }
      }

      public function offsetExists($offset) {
        return isset($this->container[$offset]);
      }

      public function offsetUnset($offset) {
        unset($this->container[$offset]);
      }

      public function offsetGet($offset) {
        return isset($this->container[$offset]) ? $this->container[$offset] : null;
      }

      function rewind() {
        $this->position = 0;
      }

      function current() {
        return $this->container[$this->position];
      }

      function key() {
        return $this->position;
      }

      function next() {
        ++$this->position;
      }

      function valid() {
        return isset($this->container[$this->position]);
      }
}