Shorter way to write multiple if-then-else-if

Question

if($row['best']){
    $id = $row['best'];
} elseif($row['average']){
    $id = $row['average'];
} elseif($row['bad']){
    $id = $row['bad'];
} 

If row['best'] is null, I need $id to equal the 2nd best. If 2nd best is null, $id is equal to the next best.

Answer 1

Simon has already answered while I was writing something similar:

foreach(array('best', 'average', 'bad') as $rank) {
  if($row[$rank]) {
    $id = $row[$rank];
    break;
  }
}

Note however, that in both this and Simon's answer, there is a possibility of $id never being assigned a value. Konijn's answer avoids that (although $id might still end up false'y)

Answer 2

How has no one mentioned the Elvis operator?!

$id = $row['best'] ?: $row['average'] ?: $row['bad'] ?: null;

Substitute your desired "not present" value of choice for null.

Edit: This is the short form of the ternary operator which evaluates to the first expression if truthy or the second expression if not. This is similar to how the || operator is often used in JavaScript.

var options = options || {};

Answer 3

You may want to write the first_in($arr, $keys) function, and rewrite your code as:

$id = first_in($row, array('best', 'average', 'bad'));

Or more common firstof($arr) function:

$id = firstof(array($row['best'], $row['average'], $row['bad'));

for example, the firstof function:

function firstof($arr) {
    foreach ($arr as $key=>$val)
       if ($val)
           return $val;
    return $arr[count($arr)-1];
}

Answer 4

From here:

If there are only 3 possibilities, you could do this:

$id = $row['best'] or $id = $row['average'] or $id = $row['bad'];

This is the closest that PHP can come to JS short circuit assignments.

Answer 5

There are some different approaches possible here, one of them is to use an array:

$arr = array($row['best'], $row['average'], $row['bad']);
for ($arr as $value) {
    if ($value) {
       $id = $value;
       break;
    }
}

If you consider this as a better way or not to do what you are trying to accomplish, is really up to you. I can imagine that if the possible options will be extended, then this would be really helpful. But for only three items, your current way is not that bad.

Answer 6

Maybe use array functions a bit?

$keys = array_keys($row, TRUE); // returns all keys for which value is boolean TRUE
$id = $keys[0]; // takes first one as ID

Note that this assume only one of the values is set to true or that keys are ordered from the one you want to get the most to one you want the least. It's often a safe assumption, but assumption none the less. Thus, my code is not an universal replacement of your original code, but in many real-life situations it would be pretty good - and it frees you from duplicating lists of possible keys in different parts of the script.