CommaSeparatedIntegers

Ensure that variable is string with comma separated integers and transform it to array of integers on success

Correct:

assure($x = '1,2,3,4', 'commaSeparatedIntegers'); // $x => [1,2,3,4]
assure($x = '1', 'commaSeparatedIntegers');       // $x => [1]
assure($x = '1,', 'commaSeparatedIntegers');      // $x => [1]
assure($x = ',1', 'commaSeparatedIntegers');      // $x => [1]
assure($x = 1, 'commaSeparatedIntegers');         // $x => [1]
assure($x = 0, 'commaSeparatedIntegers');         // $x => [0]
assure($x = '0', 'commaSeparatedIntegers');       // $x => [0]

Incorect:

assure($x = [], 'commaSeparatedIntegers');
assure($x = null, 'commaSeparatedIntegers');
assure($x = '', 'commaSeparatedIntegers');
assure($x = 'a,2,3,4', 'commaSeparatedIntegers');

All above method calls will throw \InvalidArgumentException