PHP Associative Array Duplicate Keys

Question

I have an associative array, however when I add values to it using the below function it seems to overwrite the same keys. Is there a way to have multiple of the same keys with different values? Or is there another form of array that has the same format?

I want to have:

42=>56
42=>86
42=>97
51=>64
51=>52
etc etc

Code:

   function array_push_associative(&$arr) {
       $args = func_get_args();
       foreach ($args as $arg) {
           if (is_array($arg)) {
               foreach ($arg as $key => $value) {
                   $arr[$key] = $value;
                   $ret++;
               }
           }else{
               $arr[$arg] = "";
           }
       }
       return $ret;
    }

what is the meaning of these numeric keys?

Your Common Sense
– Your Common Sense

2010-05-21 02:09:44 +00:00
Commented May 21, 2010 at 2:09 — Your Common Sense
– Your Common Sense, Commented May 21, 2010 at 2:09

Amber · Accepted Answer · 2010-05-21 01:56:28Z

40

No, you cannot have multiple of the same key in an associative array.

You could, however, have unique keys each of whose corresponding values are arrays, and those arrays have multiple elements for each key.

So instead of this...

42=>56 42=>86 42=>97 51=>64 51=>52

...you have this:

Array (
    42 => Array ( 56, 86, 97 )
    51 => Array ( 64, 52 )
)

answered May 21, 2010 at 1:56

Amber

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Comments

simhumileco · Accepted Answer · 2022-11-04 22:01:57Z

8

A key is an extension of a variable. If you overwrite the variable... You overwrite the variable.

edited Nov 4, 2022 at 22:01

simhumileco

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answered May 21, 2010 at 1:56

Mark Tomlin

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Comments

Aris · Accepted Answer · 2013-05-23 18:25:34Z

5

No, you cannot have. A workaround I use is to have each key/value pair as a new array with 2 elements:

$test = array(
     array(42,56),
     array(42,86),
     array(42,97),
     array(51,64),
     array(51,52)
)

For example, you can access the second key (=42) using:

$test[1][0]

and the second value(=86) using:

 $test[1][1]

answered May 23, 2013 at 18:25

Aris

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3 Comments

Fabien Haddadi Over a year ago

while the end result of the var assignment can't show multiple keys, you may still define them at definition time. Example: $mytab = array('a' => 'valA', 'b' => 'valB', 'a' => 'anotherValA'); The behaviour to expect then is that the last who speaks is right. You would end up with this array: { a => anotherValA, b => valB}

Aris Over a year ago

@FabienHaddadi what is the reason to do this, since the first will be overwritten by the second? this is an intentional bug.

Fabien Haddadi Over a year ago

no valid reason! Bad practice. It's just possible, period :-) I just fixed that in my Client's code a few hours ago...

Michael · Accepted Answer · 2019-01-31 05:14:36Z

I found this question while researching the exact opposite intended outcome, I have an array of data that has duplicate keys! Here's how I did it (still trying to figure out where in my process things are messing up).

$session = time();
$a = array();
$a[(string)$session] = 0;
$j = json_encode($a,JSON_FORCE_OBJECT);
print_r($a);
/* output:
Array
(
    [1510768034] => 0
)
*/
var_dump($a);
/* output:
array(1)
(
    [1510768034] =>   int(0)
)
*/
print_r($j);
/* output:
{"1510768034":0}
*/
$a = (array)json_decode($j);
$session = @array_pop(array_keys($a));
$a[(string)$session] = 10;
$j = json_encode($a,JSON_FORCE_OBJECT);
print_r($a);
/* output:
Array
(
    [1510768034] => 0
    [1510768034] => 10
)
*/
var_dump($a);
/* output:
array(2)
(
    '1510768034' => int(0)
    [1510768034] => int(10)
)
*/
print_r($j);
/* output:
{"1510768034":0,"1510768034":10}
*/

Yup....that just happened.

PHP 7.1

Edit: It's similar in PHP 7.2.10, except json_encode no longer entertains duplicate keys, encoded strings are correct. The array, however, can have matching string and integer keys.

LΞИIИ · Accepted Answer · 2016-05-29 08:31:12Z

i had the same need too create an array with the same keys, (just to keep performance by using two loops rather than 4 loops).

by using this : [$increment."-".$domain_id] => $article_id; my list of articles in each domain looks like this after a print_r() :

$AllSa  = Array
(
    [1-5] => 143
    [2-5] => 176
    [3-5] => 992
    [4-2] => 60
    [5-2] => 41
    [6-2] => 1002
    [4-45] => 5
    [5-45] => 18
    [6-45] => 20
)

And then by looping through this table to associate article by domain :

$AssocSAPerDomain = array();
    $TempDomain       = "";
    $TempDomain_first = 0;
    foreach($tree_array as $id_domain => $id_sa){
        if( !$TempDomain && $TempDomain_first == 0 ){  $TempDomain = substr(strrchr($id_domain, "-"), 1); $TempDomain_first = 1; }
        $currentDomain = substr(strrchr($id_domain, "-"), 1);
        //if($TempDomain == $currentDomain) 
        $AssocSAPerDomain[$currentDomain][] = $id_sa;
        $TempDomain = substr(strrchr($id_domain, "-"), 1);
    }

you get this

$assoc= Array
(
    [5] => 143
        => 176
        => 992
    [2] => 60
        => 41
        => 1002
    [45]=> 5
        => 18
        => 20
)

General Grievance · Accepted Answer · 2022-11-02 12:25:46Z

0

it is not possible technically. But I created a fun way to do it. Be alert, this answer is just for the fun, the ultimate goal is to get the output anyway.

So here is the answer. You first need to convert to the whole array to the string. Then the rest of the things is just string replace and a little code.

<?php

$ary="array('a'=>123,'a'=>161,'a'=>195)";

$str = str_replace("array(", "", $ary);
$str = str_replace(")", "", $str);
$arr = explode(",",$str);

foreach($arr as $element){
    $element = str_replace("=>", "", $element);
    $element = str_replace("'", "", $element);

    echo $element.'<br>';
}
?>

Here is the output

edited Nov 2, 2022 at 12:25

General Grievance

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answered Jan 21, 2020 at 5:48

santosh devnath

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2 Comments

fahim152 Over a year ago

After seeing your solution... I'm really confused should I give it a up vote or not ! :v

santosh devnath Over a year ago

@fahim152 ha ha. it is up to you. I just showed a way to do it for an emergency purpose. Because technicaly it is not possible but if you are in a crital situation and really wanted to do it anyway, then this is for you. Thanks

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