Substitute column value in each row of a 2d array based on other rows in the same array-CodePudding

I have an array like so:

$array = [
    ['record' => 1, 'sponsor' => 2, 'email' => '[email protected]'],
    ['record' => 2, 'sponsor' => 2, 'email' => '[email protected]'],
    ['record' => 3, 'sponsor' => 2, 'email' => '[email protected]'],
    ['record' => 4, 'sponsor' => 2, 'email' => '[email protected]'],
];

Each row has a unique record and email and the sponsor key is related to the record. So, instead of an integer, I am trying to replace the value of the sponsor key with the corresponding email based on the record, something like this:

$array = [
    ['record' => 1, 'sponsor' => '[email protected]', 'email' => '[email protected]'],
    ['record' => 2, 'sponsor' => '[email protected]', 'email' => '[email protected]'],
    ['record' => 3, 'sponsor' => '[email protected]', 'email' => '[email protected]'],
    ['record' => 4, 'sponsor' => '[email protected]', 'email' => '[email protected]'],
];

I have tried using a foreach loop but it doesn't give me the expected result:

$yes = [];
foreach ($array as $key => $arr) {
    if ( ! empty($arr['sponsor']) ) {
        if ( $arr['sponsor'] == $array[$key]['record'] ) {
            $yes[] = ['sponsor' => $array[$key]['email']];
        }
    }
    $yes[] = [
        'record' => $array[$key]['record'], 
        'email' => $array[$key]['email'],
        'sponsor' => $array[$key]['sponsor'],
    ];
}
print_r($yes);

CodePudding user response：

As record is unique, I recommend rebuilding $arr using this value as the key. Then you loop again to replace your value for $sponsor –

$indexedArray = [];
foreach ($array as $v) {
  $indexedArray[$v['record']] = $v;
}   
foreach ($indexedArray as $record => $v) {
  if (isset($indexedArray[$v['sponsor']]) && isset($indexedArray[$v['sponsor']]['email'])) {
    $indexedArray[$record]['sponsor'] = $indexedArray[$v['sponsor']]['email'];
  }
}
$yes = array_values($indexedArray);

CodePudding user response：

Create a lookup array with record values as keys and email values as values, then overwrite the sponsor value in each row based on the corresponding lookup value.

Code: (Demo)

$lookup = array_column($array, 'email', 'record');
var_export(
    array_map(fn($row) => array_replace($row, ['sponsor' => $lookup[$row['sponsor']]]), $array)
);

Or with a classic loop: (Demo)

$lookup = array_column($array, 'email', 'record');
foreach ($array as &$row) {
    $row['sponsor'] = $lookup[$row['sponsor']];
}
var_export($array);

If there is a chance that a given sponsor value might not be found in the lookup, then use $lookup[$row['sponsor']] ?? 'some fallback' when you try to access the lookup array. This way you will not generate warnings/errors. This is a more concise way of checking isset().

p.s. Bear in mind that using the array union operator won't work properly in this case.