ArrayOfStrings

Ensure that variable is an array with elements that can be treated as string. Each element of array is validated and converted to string on success.

Correct:

assure($x = 'a', 'arrayOfStrings');                     // $x = ['a']
assure($x = 1, 'arrayOfStrings');                       // $x = ['1']
assure($x = [1, 'two'], 'arrayOfStrings');              // $x = ['1', 'two']
assure($x = (object)['one', 'two'], 'arrayOfStrings');  // $x = ['one', 'two']

Incorect:

assure($x = [], 'arrayOfStrings');
assure($x = [null], 'arrayOfStrings');
assure($x = 1, 'arrayOfStrings');
assure($x = [1,'a'], 'arrayOfStrings');
assure($x = (object)[1,'a'], 'arrayOfStrings');

All above method calls will throw \InvalidArgumentException