从PHP中的列表中选择第一个非空值

Question

Assuming $a , $b , $c , $d , $e be some random unknown values. I'd like to pick one value from them which is not empty with priority in that order.

To be brief, I want to achieve the same result as in javascript return $a || $b || $c || $d || $e || 0; return $a || $b || $c || $d || $e || 0; does.

Currently, in PHP we use (parenthesis are just for readability):

return $a ? $a : ($b ? $b : ($c ? $c : ($d ? $d : ($e ? $e : 0))));

Or since PHP 5.3

return $a ?: $b ?: $c ?: $d ?: $e ?: 0;

I can see the 5.3 syntax is lighter and almost similar to that of JavaScript. But I wonder if there is something more elegant available in PHP.

The other question marked as duplicate to this asks for a solution to do this. But here I am asking for improvement in case there is something available in PHP natively. This is to ensure we use best possible solution for the said problem.

Answer 1

You can use the following function:

function firstNonEmpty(array $list) {
  foreach ($list as $value) {
    if ($value) {
      return $value;
    }
  }
  return null;
}

Then call it like that:

$value = firstNonEmpty([0, null, 3, 2]);

Answer 2

My original question is about some native feature that allows easy pick mechanism for a set of variables. I already indicated that the short ternary operator syntax does it.

However, from the above answers and lot of search around I come to the conclusion that the ternary syntax is the shortest available method in PHP to achieve the said result.

I was expecting something like pick($a, $b, $c, $d, $e, ....); , similar to COALESCE(colname, 0) of SQL but sadly no such function exists yet, AFAIK.

---

Since people are answering with custom functions for this, I tend to put my version of such custom functions.

/**
 * Function to pick the first non-empty value from the given arguments
 * If you want a default value in case all of the given variables are empty,  
 * pass an extra parameter as the last value.
 *
 * @return  mixed  The first non-empty value from the arguments passed   
 */
function coalesce()
{
    $args = func_get_args();

    while (count($args) && !($arg = array_shift($args)));

    return isset($arg) ? $arg : null;
}

You can call above function with any number of arguments , like:

$value = coalesce($a, $b, $c, $d, $e, 0);

Or, if you have an array instead of independent variables:

// Assuming, $array = array($a, $b, $c, $d, $e);
$value = call_user_func_array('coalesce', $array);

Or define another function for array arguments if you like. @gothdo did this pretty well. Just add a default value for fallback and its good to go.

/**
 * Function to pick the first non-empty value from the given array
 * If you want a default value in case all of the values in array are empty,  
 * pass the default value as the second parameter.
 *
 * @param   array  $args     The array containing values to lookup
 * @param   mixed  $default  The default value to return
 *
 * @return  mixed  The first non-empty value from the arguments passed   
 */
function coalesce_array(array $args, $default = null)
{
    while (count($args) && !($arg = array_shift($args)));

    return isset($arg) ? $arg : $default;
}

---

I still prefer the ternary syntax, because no other approach will work as good if the variable is not defined at all, and we want to check isset instead of empty or truthy value.

See the below case. We cannot pass $a , $b etc... to a function unless we are sure it is defined, otherwise it will raise error.

$value = isset($a) ? $a : isset($b) ? $b : isset($c) ? $c : 0;

Looks dirty, but its consistent and straight forward. Plus, native approach is usually better on performance.

Well, in PHP 7 , you can use null coalescing operator like:

 $value = $a ?? $b ?? $c ?? 0;

This checks isset internally. Pretty clean! Right?