Re: Build index array

On Mon, Dec 20, 2021 at 1:08 AM Yves Goergen via php-general <
[email protected]> wrote:

> Hello,
>
> I'm looking for a PHP function that takes an array of objects
> (associative arrays) and changes the keys to one of the subvalues. You
> probably won't understand this, so I'll give an example.
>
> Here's the source data:
>
> [
>    [
>      'col1' => 'val1a',
>      'col2' => 'val2a',
>      'col3' => 'val3a'
>    ],
>    [
>      'col1' => 'val1b',
>      'col2' => 'val2b',
>      'col3' => 'val3b'
>    ],
>    [
>      'col1' => 'val1c',
>      'col2' => 'val2c',
>      'col3' => 'val3c'
>    ]
> ]
>
> The desired result for the index key 'col1' is:
>
> [
>    'val1a' => [
>      'col1' => 'val1a',
>      'col2' => 'val2a',
>      'col3' => 'val3a'
>    ],
>    'val1b' => [
>      'col1' => 'val1b',
>      'col2' => 'val2b',
>      'col3' => 'val3b'
>    ],
>    'val1c' => [
>      'col1' => 'val1c',
>      'col2' => 'val2c',
>      'col3' => 'val3c'
>    ]
> ]
>
> All subarrays are still there (the order doesn't matter) but their keys
> are changed from 0, 1, 2... to the value of their 'col1' entry so I can
> access each subarray quickly and easily (and efficiently?) by its ID or
> name or whatever.
>
> That's similar to .NET LINQ's ToDictionary method that takes a key
> selector delegate and builds exactly this structure. It can be used to
> convert an ordinary database query result to a lookup dictionary.
>
> I know I can write this in a handful of lines of code, but I need this
> on a regular basis so before I roll my own version, I want to make sure
> I haven't missed something that's already there. Preferably for PHP 7.4
> and newer.
>
> -Yves
>

Hi Yves,

>> changes the keys to one of the subvalues
This is ambiguous, there is no ready function and you will have to write
one.

E.g.

function customFunction($array){
    $output = [];
    foreach($array as $i => $blob){
        foreach($blob as $key => $value){
            $output[$value] = $blob;
            continue 2;
        }
    }
    return $output;
}

$input = [
   [
     'col1' => 'val1a',
     'col2' => 'val2a',
     'col3' => 'val3a'
   ],
   [
     'col1' => 'val1b',
     'col2' => 'val2b',
     'col3' => 'val3b'
   ],
   [
     'col1' => 'val1c',
     'col2' => 'val2c',
     'col3' => 'val3c'
   ]
];

$output = customFunction($input);

echo json_encode($output);

=========

{
   "val1a":{
      "col1":"val1a",
      "col2":"val2a",
      "col3":"val3a"
   },
   "val1b":{
      "col1":"val1b",
      "col2":"val2b",
      "col3":"val3b"
   },
   "val1c":{
      "col1":"val1c",
      "col2":"val2c",
      "col3":"val3c"
   }
}

-- 
- Jigar