使用引用复制数组; 如何只获取值

Question

I was messing with arrays and references, when I came across an interesting problem. Take this code, for example:

// Set everything up
$testArray = array(
    'a' => array(),
    'b' => array()
);

$saved = array();

$ref =& $testArray['b'];

// Set a value via the reference
$ref = array(1);

// Save the current array state
$saved[] = $testArray; // This shouldn't be a reference, right?

// Set another value via the reference
$ref = array(2);

// Save the current array state
$saved[] = $testArray; // This shouldn't be a reference, right?

Nothing too complicated. It makes an array, and a reference to a "deep value" in the array.

When I var_dump($saved), the result is not what I expect! I get:

array(2) {
  [0]=>
  array(2) {
    ["a"]=>
    array(0) {
    }
    ["b"]=>
    &array(1) {
      [0]=>
      int(2)
    }
  }
  [1]=>
  array(2) {
    ["a"]=>
    array(0) {
    }
    ["b"]=>
    &array(1) {
      [0]=>
      int(2)
    }
  }
}

I thought arrays were copied by value, not reference. Why is [b] equal to array(2) in both spots? How can I copy an array and break its references?

I want the result to be:

array(2) {
  [0]=>
  array(2) {
    ["a"]=>
    array(0) {
    }
    ["b"]=>
    array(1) {
      [0]=>
      int(1)
    }
  }
  [1]=>
  array(2) {
    ["a"]=>
    array(0) {
    }
    ["b"]=>
    array(1) {
      [0]=>
      int(2)
    }
  }
}

Why is $ref still linked to a copy of the $testArray array? I want to basically save the "state" of the array, and have the reference only update the original and not the copy.

Answer 1

Your array contains arrays' references, if you copy your array, the sub-arrays are just references... you need a deep copy. Make a recursive function:

function cloneArray($array){
    $newArray = array();

    foreach($array as $key => $value){
        if(is_array($value))
            $value = cloneArray($value);

        $newArray[$key] = $value;
    }

    return $newArray;
}

this should work for your needs