What is the best way to check if array has values other than null in php?

Question

In PHP empty([null, null, null]) will obviously return false .

What is the best way from the performance point of view to detect that an array contains only null values?

Answer 1

Performance testing of the answers so far using this code, first with an array of 1000 null values, then an array with 999 null values and one (random) non-null value:

$array = array_fill(0, 1000, null);
$elapsed = array();
foreach (array('Nick1', 'Nick2', 'Eddie', 'Vivek') as $func) {
    $start = explode(' ', microtime());
    for ($i = 0; $i < 10000; $i++) $func($array);
    $elapsed[$func] = elapsed_time($start);
}

In the tables, Nick1 = array_reduce , Nick2 = count(array_filter) , Vivek = for (aka Nick3).

Results (all null array):

Function    Elapsed Time    Delta
Vivek       0.654           0%
Nick2       0.886           35%
Nick1       0.964           47%
Eddie       3.122           377%

Results (array with 999 null values, 1 random non-null value, different each iteration)

Function    Elapsed Time    Delta
Vivek       0.305           0%
Nick2       0.888           191%
Nick1       0.891           192%
Eddie       3.114           921%

As can be seen for the all- null array, the for loop is considerably faster, mainly because it doesn't suffer the overhead of a function call for each value. For the array with one non- null value, it's even faster as it can break as soon as it finds a non- null value.

Leave a comment if you want your answer to be added to the test...

Answer 2

One option is using array_unique to get all unique array values. If there is only one element and that element is null, all elements are null.

$unique = array_unique( [null, null, null] );

if ( count( $unique ) === 1 && $unique[0] === null ) {
    //All Null
} else {
    //Not all Null
}

Answer 3

Here's a couple of ways to determine that an array only contains null values:

$array = array(null, null, null);
echo array_reduce($array, function ($c, $v) { return $c && is_null($v); }, true) ? 'empty' : 'not empty';
echo !count(array_filter($array, function($v) { return !is_null($v); })) ? 'empty' : 'not empty';

Output:

empty
empty

And then of course we have the humble for loop:

$c = count($array);
for ($i = 0; $i < $c; $i++) {
    if (!is_null($array[$i])) {
        echo "not empty";
        break;
    }
}
if ($i == $c) echo "empty";

Demo on 3v4l.org

Answer 4

$arrayIsNull = ($array = array_unique([null, null, null])) && (next($array) === false && is_null($array[0]));