Question 41270 in PHP Question posted in
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Is it possible to append nothing to an array? – PHP

I am wondering if it is possible to append "nothing" to an array, i.e. the array won’t be affected. The scenario is that I would like to use the ? : operators to append values to an array if it exists. Otherwise nothing should be appended. I am aware that I can solve this with an ordinary if statement without the else part. But is there a way to tell PHP that it should append "nothing"? I’m just curious if there’s a method for this?

<?php
$source_arr = ["Car" => "Volvo", "City" => "Stockholm", "Country" => "Sweden"];
$new_arr    = [];

$new_arr[] = (key_exists("Car",   $source_arr)) ? $source_arr["Car"]   : [];
$new_arr[] = (key_exists("State", $source_arr)) ? $source_arr["State"] : [];  
// An ordinary if statement works of course:
// if (key_exists("State", $source_arr)) { $new_arr[] = $source_arr["State"]; }
// But, is it possible to use ? : and append "nothing" (i.e. not using []) if key doesn't exist?

echo "<pre>";
var_export($new_arr);
echo "</pre>";

// The above outputs (and I understand why):
//   array (
//    0 => 'Volvo',
//    1 => 
//    array (
//    ),
//  )
// 
// But I want the following result (but I don't know if it's possible with ? :)
//   array (
//     0 => 'Volvo',
//   )

?>
Tags:

4

Answers


  1. 0

    You can’t do it when assigning to $array[]. You can do it with a function that takes an array argument, by wrapping the value to be added in an array, and using an empty array as the alternate value. array_merge() is such a function.

    $new_array = array_merge($new_array, 
    key_exists("Car", $source_arr) ? [$source_arr["Car"]] : [],
    key_exists("State", $source_arr) ? [$source_arr["State"]] : []
);
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  2. 0

    You could always add the new value (i.e., even if it’s empty) and then remove the empties with array_filter() when you’re done adding:

    $new_arr = array_filter([
    $source_arr["Car"] ?? null,
    $source_arr["State"] ?? null,
]);

    Of course, the problem here is that you’ll never be able to rely on what’s in the array. Is the first element car? Is it city? Country? You’ll never know.

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  3. 0

    Even better, get everything in one line using array_intersect_key

    $source_arr = ["Car" => "Volvo", "City" => "Stockholm", "Country" => "Sweden"];
$new_arr    = array_intersect_key($source_arr, ['Car'=>'','State'=>'']);

var_export($new_arr);

    The above outputs the following:

    array (
  'Car' => 'Volvo',
)

    If you really do want a non-associative, indexed array, just pass the result of array_intersect_key to array_values:

    $new_arr = array_values(array_intersect_key($source_arr, ['Car'=>'','State'=>'']));

    array (
  0 => 'Volvo',
)

    Check both methods here.

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  4. 0

    Yes, you absolutely can "push nothing" conditionally.

    Use the splat operator to unpack an array with zero or one element in it.

    Code: (Demo)

    $source_arr = ["Car" => "Volvo", "City" => "Stockholm", "Country" => "Sweden"];
$new_arr    = [];

array_push(
    $new_arr,
    ...key_exists("Car",   $source_arr) ? [$source_arr["Car"]] : [],
    ...key_exists("State", $source_arr) ? [$source_arr["State"]] : []
);

var_export($new_arr);
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