翻译强力驱动Why the following
$a = new SplFixedArray(5); $a[0] = array(1, 2, 3); $a[0][0] = 12345; // here var_dump($a);produces
Notice: Indirect modification of overloaded element of SplFixedArray has no effect in on line Is it a bug? How do you deal with multidimensional SplFixedArrays then? Any workarounds?
First, the problem is related to all classes which implement ArrayAccess it is not a special problem of SplFixedArray only.
When you accessing elements from SplFixedArray using the [] operator it behaves not exactly like an array. Internally it's offsetGet() method is called, and will return in your case an array - but not a reference to that array. This means all modifications you make on $a[0] will get lost unless you save it back:
Workaround:
$a = new SplFixedArray(5); $a[0] = array(1, 2, 3); // get element $element = $a[0]; // modify it $element[0] = 12345; // store the element again $a[0] = $element; var_dump($a);Here is an example using a scalar which fails too - just to show you that it is not related to array elements only.
This is actually fixable if you slap a & in front of offsetGet (assuming you have access to the internals of your ArrayAccess implementation):
class Dict implements IDict { private $_data = []; /** * @param mixed $offset * @return bool */ public function offsetExists($offset) { return array_key_exists(self::hash($offset), $this->_data); } /** * @param mixed $offset * @return mixed */ public function &offsetGet($offset) { return $this->_data[self::hash($offset)]; } /** * @param mixed $var * @return string */ private static function hash($var) { return is_object($var) ? spl_object_hash($var) : json_encode($var,JSON_UNESCAPED_SLASHES); } /** * @param mixed $offset * @param mixed $value */ public function offsetSet($offset, $value) { $this->_data[self::hash($offset)] = $value; } /** * @param mixed $offset */ public function offsetUnset($offset) { unset($this->_data[self::hash($offset)]); } }Adding my experience with the same error, in case it helps anyone:
I recently imported my code into a framework with a low error-tolerance (Laravel). As a result, my code now throws an exception when I try to retrieve a value from an associative array using a non-existent key. In order to deal with this I tried to implement my own dictionary using the ArrayAccess interface. This works fine, but the following syntax fails:
$myDict = new Dictionary(); $myDict[] = 123; $myDict[] = 456;And in the case of a multimap:
$properties = new Dictionary(); $properties['colours'] = new Dictionary(); $properties['colours'][] = 'red'; $properties['colours'][] = 'blue';I managed to fix the problem with the following implementation:
dict = []; } // INTERFACE IMPLEMENTATION - ArrayAccess public function offsetExists($key) { return array_key_exists($key, $this->dict); } public function offsetGet($key) { if ($this->offsetExists($key)) return $this->dict[$key]; else return null; } public function offsetSet($key, $value) { // NOTE: THIS IS THE FIX FOR THE ISSUE "Indirect modification of overloaded element of SplFixedArray has no effect" // NOTE: WHEN APPENDING AN ARRAY (E.G. myArr[] = 5) THE KEY IS NULL, SO WE TEST FOR THIS CONDITION BELOW, AND VOILA if (is_null($key)) { $this->dict[] = $value; } else { $this->dict[$key] = $value; } } public function offsetUnset($key) { unset($this->dict[$key]); } }Hope it helps.
I guess SplFixedArray is incomplete/buggy.
If i wrote an own class and it works like a charm:
$a = new \myArrayClass(); $a[0] = array(1, 2, 3); $a[0][0] = 12345; var_dump($a->toArray());Output (no notices/warnings here, in strict mode too):
array (size=1) 0 => array (size=3) 0 => int 12345 1 => int 2 2 => int 3Using the [] operator is not a problem (for assoc/mixed arrays too). A right implementation of offsetSet should do the job:
public function offsetSet($offset, $value) { if ($offset === null) { $offset = 0; if (\count($this->array)) { $keys = \preg_grep( '#^(0|([1-9][0-9]*))$#', \array_keys($this->array)); if (\count($keys)) { $offset = \max($keys) + 1; } } } ...But there is only one exception. Its not possible to use the [] operator for offset which does not exist. In our example:
$a[1][] ='value'; // Notice: Indirect modification of overloaded...It would throw the warning above because ArrayAccess calls offsetGet and not offsetSet for [1] and the later [] fails. Maybe there is a solution out there, but i did not find it yet. But the following is working without probs:
$a[] ='value'; $a[0][] ='value';I would write an own implementation instead of using SplFixedArray. Maybe its possible to overload some methods in SplFixedArray to fix it, but i am not sure because i never used and checked SplFixedArray.