Question

How do you verify an array contains only values that are integers?

I’d like to be able to check an array and end up with a boolean value of true if the array contains only integers and false if there are any other characters in the array. I know I can loop through the array and check each element individually and return true or false depending on the presence of non-numeric data:

For example:

$only_integers = array(1,2,3,4,5,6,7,8,9,10);
$letters_and_numbers = array('a',1,'b',2,'c',3);

function arrayHasOnlyInts($array)
{
    foreach ($array as $value)
    {
        if (!is_int($value)) // there are several ways to do this
        {
             return false;
        }
    }
    return true;
}

$has_only_ints = arrayHasOnlyInts($only_integers ); // true
$has_only_ints = arrayHasOnlyInts($letters_and_numbers ); // false

But is there a more concise way to do this using native PHP functionality that I haven’t thought of?

Note: For my current task I will only need to verify one dimensional arrays. But if there is a solution that works recursively I’d be appreciative to see that to.

Answer 1

$only_integers       === array_filter($only_integers,       'is_int'); // true
$letters_and_numbers === array_filter($letters_and_numbers, 'is_int'); // false

It helps to define two helper, higher-order functions:

/**
 * Tell whether all members of $elems validate the $predicate.
 *
 * all(array(), 'is_int')           -> true
 * all(array(1, 2, 3),   'is_int'); -> true
 * all(array(1, 2, 'a'), 'is_int'); -> false
 */
function all($elems, $predicate) {
  foreach ($elems as $elem) {
    if (!call_user_func($predicate, $elem)) {
      return false;
    }
  }

  return true;
}

/**
 * Tell whether any member of $elems validates the $predicate.
 *
 * any(array(), 'is_int')               -> false
 * any(array('a', 'b', 'c'), 'is_int'); -> false
 * any(array(1, 'a', 'b'),   'is_int'); -> true
 */
function any($elems, $predicate) {
  foreach ($elems as $elem) {
    if (call_user_func($predicate, $elem)) {
      return true;
    }
  }

  return false;
}