Adding field on array on PHP [duplicate]

When dealing with $row in the foreach loop you aren't dealing with the same variable that is in the array, but a copy. If you want to make lasting changes you need to use a reference.

function addLength($toAdd, $added){
   $result = $toAdd;
    foreach ($result as & $row) {
        foreach ($added as $key => $value) {
            if($key == $row['id'] ){
                $row['length'] = $value;   
            }
        } 
    }
    var_dump($result);
    return $result;
}

Please make sure to note that a reference will still exist after the foreach loop has completed. It will contain a reference to the last element of your $result array. To stop this you would need to manually unset the reference.

    function addLength($toAdd, $added){
   $result = $toAdd;
    foreach ($result as & $row) {
        foreach ($added as $key => $value) {
            if($key == $row['id'] ){
                $row['length'] = $value;   
            }
        } 
    }
    var_dump($row); // Outputs the last element of your $result array
    unset($row);
    var_dump($row); // Now undefined.

    var_dump($result);
    return $result;
}

Just as an FYI, you can optimise your code and get rid of the second foreach loop, it's just not necessary. This would do the same:

function addLength($toAdd, $added){
   $result = $toAdd;
    foreach ($result as & $row) {
        if ( array_key_exists($row['id'], $added) ) {
            $row['length'] = $added[$row['id']];
        }
    }
    var_dump($result);
    return $result;
}

Now rather than looping through $added for every item in $toAdd you just check to see if the data is there (by checking for the array key) and if it is, use it.

foreach copies each element of the array into a variable, so your changes have no effect. Update the original array instead:

function addLength($toAdd, $added){
   $result = $toAdd;
    foreach ($result as $outerKey => $row) {
        foreach ($added as $key => $value) {
            if($key == $row['id'] ){
                $result[$outerKey]['length'] = $value;   
            }
        } 
    }
    var_dump($result);
    return $result;
}

i think you want to add this type change

function addLength($toAdd, $added){
 $result = $toAdd;
 foreach ($result as $first_key => $row) {
    foreach ($added as $key => $value) {
        if($key == $row['id'] ){
            $result[$first_key]['length'] = $value;   
        }
    } 
}
var_dump($result);
return $result;
}

if you do not add key value in index then you can use this code

 function addLength($toAdd, $added){
 $result = $toAdd;
 foreach ($result as $first_key => $row) {
    foreach ($added as $key => $value) {
        if($key == $row['id'] ){
            $result[]['length'] = $value;   
        }
    } 
}
var_dump($result);
return $result;
}

Change the line:

$row['length'] = $value;  

to:

$result[$row]['length'] = $value;

If that doesn't work, you will need to change the foreach ($result as $row) loop to:

foreach ($result as $row => $data)

Correct me if in wrong but ($result as $row) assigns $row to a copy of an element in $result. It is not referencing the original element in $result. Try foreach($result as &$row) If you do use a reference variable in a foreach loop remember to unset it after the loop with unset($row).