array_product

This function can be used to test if all values in an array of booleans are TRUE.Consider:<?phpfunction outbool($test){    return (bool) $test;}$check[] = outbool(TRUE);$check[] = outbool(1);$check[] = outbool(FALSE);$check[] = outbool(0);$result = (bool) array_product($check);// $result is set to FALSE because only two of the four values evaluated to TRUE?>The above is equivalent to:<?php$check1 = outbool(TRUE);$check2 = outbool(1);$check3 = outbool(FALSE);$check4 = outbool(0);$result = ($check1 && $check2 && $check3 && $check4);?>This use of array_product is especially useful when testing an indefinite number of booleans and is easy to construct in a loop.

Here's how you can find a factorial of a any given number with help of range and array_product functions.function factorial($num) {    return array_product(range(1, $num));}printf("%d", factorial(5)); //120

Just a little correction for Andre D's answer: "(bool) array_product($array);" is equivalent with the conjunction of each array elements of $array, UNLESS the provided array is empty in which case array_product() will return 1, which will translate to boolean TRUE.To mitigate this, you should expand the function with an additional check:<?php$result = !empty($check) && !!array_product($check);?>

You can use array_product() to calculate the geometric mean of an array of numbers:  <?php$a = [ 1, 10, 100 ];$geom_avg = pow( array_product( $a ), 1 / count( $a ));// = 9.999999999999998 ≈ 10?>

You can use array_product to calculate the factorial of n:
<?php
function factorial( $n )
{
  if( $n < 1 ) $n = 1;
  return array_product( range( 1, $n ));
}
?>

If you need the factorial without having array_product available, here is one:
<?php
function factorial( $n )
{
  if( $n < 1 ) $n = 1;
  for( $p++; $n; ) $p *= $n--;
  return $p;
}
?>