phparrays

PHP copy reference from array to array

Codes:

$a = array('email'=>'orange@test','topic'=>'welcome onboard','timestamp'=>'2017-10-6');

$b = array();
foreach($a as $v){
    $b[] = &$v;
}

var_dump($a);
var_dump($b);

Result:

array(3) {
  ["email"]=>
  string(11) "orange@test"
  ["topic"]=>
  string(15) "welcome onboard"
  ["timestamp"]=>
  string(9) "2017-10-6"
}
array(3) {
  [0]=>
  &string(9) "2017-10-6"
  [1]=>
  &string(9) "2017-10-6"
  [2]=>
  &string(9) "2017-10-6"
}

Why the content of $b is not reference of each element of $a? What I expected of $b should be like {&a[0],&a[1],&a[2]} instead of {&a[2],&a[2],&a[2]}

Solution

  • Even i got error when i tried to reference key

    $a = array('email'=>'orange@test','topic'=>'welcome onboard','timestamp'=>'2017-10-6');

$b = array();
foreach($a as &$key=>&$v){
    $b[] = &$v;
}

    Fatal error: Key element cannot be a reference

    Can someone explain to me why you can't pass a key as reference?

    Because the language does not support this. You'd be hard-pressed to find this ability in most languages, hence the term key.

    So am I stuck with something like this?

    Yes. The best way is to create a new array with the appropriate keys.

    Any alternatives?

    The only way to provide better alternatives is to know your specific situation. If your keys map to table column names, then the best approach is to leave the keys as is and escape them at their time of use in your SQL.

    Re: Alternatives to Pass both Key and Value By Reference:

    Reference works only for value

    <?php

$a = array('email'=>'orange@test','topic'=>'welcome onboard','timestamp'=>'2017-10-6');

$b = array();
foreach($a as $key=>&$v){
    $b[] = &$v;
}
echo "<pre>";
print_r($a);
echo "</pre>";echo "<pre>";
print_r($b);

    Output will be

    Array
(
    [email] => orange@test
    [topic] => welcome onboard
    [timestamp] => 2017-10-6
)
Array
(
    [0] => orange@test
    [1] => welcome onboard
    [2] => 2017-10-6
)