CODEWITHSUNDEEP
phparraysmultidimensional-array
Vincent
Vincent

Reputation: 1730

How to set a list of values as keys in a multidimensional associative array?

I would like to convert a list of values such as:

$foo = ['a', 'b', 'c'];

into a list of traversing array keys such as:

$bar['a']['b']['c'] = 123;

How I can create an associative array which keys are based on a set values stored in another array?

Upvotes: 3

Views: 112

Answers (3)

mickmackusa
mickmackusa

Reputation: 47774

Here is another option: Create a temporary parsable string (by extracting the first value, then appending the remaining values as square bracket wrapped strings), call parse_str(), and set the output variable as $bar.

Code: (Demo)

$foo = ['a', 'b', 'c'];
$val=123;

parse_str(array_shift($foo).'['.implode('][',$foo)."]=$val",$bar);
// built string: `a[b][c]=123`
var_export($bar);

Output:

array (
  'a' => 
  array (
    'b' => 
    array (
      'c' => '123',
    ),
  ),
)

If that first method feels too hack-ish, the following recursive method is a stable approach:

Code: (Demo)

function nest_assoc($keys,$value){
    return [array_shift($keys) => (empty($keys) ? $value : nest_assoc($keys,$value))];
    //      ^^^^^^^^^^^^^^^^^^--------------------------------------------------------extract leading key value, modify $keys
    //  check if any keys left-----^^^^^^^^^^^^
    //  no more keys, use the value---------------^^^^^^
    //  recurse to write the subarray contents-------------^^^^^^^^^^^^^^^^^^^^^^^^^
}

$foo=['a','b','c'];
$val=123;

var_export(nest_assoc($foo,$val));
// same output

Upvotes: 0

Eaten by a Grue
Eaten by a Grue

Reputation: 22931

I would do it like this:

$foo = ['a', 'b', 'c']; 
$val = '123';
foreach (array_reverse($foo) as $k => $v) {
    $bar = [$v => $k ? $bar : $val];
}

We are iterating over the array in reverse and assigning the innermost value first, then building the array from the inside out.

Upvotes: 1

LF-DevJourney
LF-DevJourney

Reputation: 28529

You can make it with reference. Try this code, live demo

<?php
$foo = ['a', 'b', 'c']; 
$array = [];
$current = &$array;
foreach($foo as $key) {
  @$current = &$current[$key];
}
$current = 123;
print_r($array);

Upvotes: 4

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