Invalid argument supplied for foreach()

Question

It often happens to me to handle data that can be either an array or a null variable and to feed some foreach with these data.

$values = get_val         


        

Answer 1

Exceptional case for this notice occurs if you set array to null inside foreach loop

if (is_array($values))
{
    foreach ($values as $value)
    {
        $values = null;//WARNING!!!
    }
}

Answer 2

How about this solution:

$type = gettype($your_iteratable);
$types = array(
    'array',
    'object'
);

if (in_array($type, $types)) {
    // foreach code comes here
}

Answer 3

foreach ($arr ?: [] as $elem) {
    // Do something
}

This doesen't check if it is an array, but skips the loop if the variable is null or an empty array.

Answer 4

What about defining an empty array as fallback if get_value() is empty?
I can't think of a shortest way.

$values = get_values() ?: [];

foreach ($values as $value){
  ...
}

Answer 5

How about this one? lot cleaner and all in single line.

foreach ((array) $items as $item) {
 // ...
 }

Answer 6

Please do not depend on casting as a solution, even though others are suggesting this as a valid option to prevent an error, it might cause another one.

Be aware: If you expect a specific form of array to be returned, this might fail you. More checks are required for that.

E.g. casting a boolean to an array (array)bool, will NOT result in an empty array, but an array with one element containing the boolean value as an int: [0=>0] or [0=>1].

I wrote a quick test to present this problem. (Here is a backup Test in case the first test url fails.)

Included are tests for: null, false, true, a class, an array and undefined.

---

Always test your input before using it in foreach. Suggestions:

1. Quick type checking: $array = is_array($var) or is_object($var) ? $var : [] ;
2. Type hinting arrays in methods before using a foreach and specifying return types
3. Wrapping foreach within if
4. Using try{}catch(){} blocks
5. Designing proper code / testing before production releases
6. To test an array against proper form you could use array_key_exists on a specific key, or test the depth of an array (when it is one !).
7. Always extract your helper methods into the global namespace in a way to reduce duplicate code