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A short test to confirm references are preserved in cloned arrays.

// create a stdClass object (using my lazy way of coercing arrays to objects)
$object = (object) array( 'thing' => 'original' );

// add that object to an array element
$array = array( 'object_one' => $object );

// clone the array by assignment to a new variable
$array_two = $array;

// add a new copy of the original object to a new element in the new array
$array_two['object_two'] = $object;

// show what we have so far
var_dump( $object , $array , $array_two );

The result is:

object(stdClass)#1 (1) {
  ["thing"]=>
  string(8) "original"
}
array(1) {
  ["object_one"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(8) "original"
  }
}
array(2) {
  ["object_one"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(8) "original"
  }
  ["object_two"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(8) "original"
  }
}

Now let’s mess with one piece of that to check if the object was passed by reference or got cloned:

// change one of the objects in the second array
$array_two['object_two']->thing = 'array_two,object_two';

// see that all the references to that object have been changed
var_dump( $object , $array , $array_two );

Confirmed, the object is passed by reference, even though the array that contained it was cloned:

object(stdClass)#1 (1) {
  ["thing"]=>
  string(20) "array_two,object_two"
}
array(1) {
  ["object_one"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(20) "array_two,object_two"
  }
}
array(2) {
  ["object_one"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(20) "array_two,object_two"
  }
  ["object_two"]=>
  object(stdClass)#1 (1) {
    ["thing"]=>
    string(20) "array_two,object_two"
  }
}

Posted on Friday, November 23rd, 2012 at 10:16 am in Technology   |  RSS feed |   Respond   |   Trackback URL