array_product

(PHP 5 >= 5.1.0)

array_productCalculate the product of values in an array

Description

number array_product ( array $array )

array_product() returns the product of values in an array.

Parameters

array

The array.

Return Values

Returns the product as an integer or float.

Changelog

Version Description
5.3.6 The product of an empty array is now 1, when before this function would return 0 for an empty array.

Examples

Example #1 array_product() examples

<?php

$a 
= array(2468);
echo 
"product(a) = " array_product($a) . "\n";
echo 
"product(array()) = " array_product(array()) . "\n";

?>

The above example will output:

product(a) = 384
product(array()) = 1

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User Contributed Notes 4 notes

up
6
Andre D
8 years ago
This function can be used to test if all values in an array of booleans are TRUE.

Consider:

<?php

function 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.
up
6
Marcel G
4 years ago
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;
}
?>
up
0
Jimmy PHP
7 months ago
array_product() can be used to implement a simple boolean AND search

<?php
$args
= array('first_name'=>'Bill','last_name'=>'Buzzard');
$values[] = array('first_name'=>'Brenda','last_name'=>'Buzzard');
$values[] = array('first_name'=>'Victor','last_name'=>'Vulture');
$values[] = array('first_name'=>'Bill','last_name'=>'Blue Jay');
$values[] = array('first_name'=>'Bill','last_name'=>'Buzzard');

$result = search_for($values,$args);
var_dump($result);exit;

function
search_for($array,$args) {
   
$results = array();
    foreach (
$array as $row) {
       
$found = false;
       
$hits = array();
        foreach (
$row as $k => $v) {
            if (
array_key_exists($k,$args)) $hits[$k] = ($args[$k] == $v);
        }

       
$found = array_product($hits);
        if (!
in_array($row,$results) && true == $found) $results[] = $row;
    }

    return
$results;
}
?>

Output:

array (size=1)
  0 =>
    array (size=2)
      'first_name' => string 'Bill' (length=4)
      'last_name' => string 'Buzzard' (length=7)
up
0
pqpqpq at wanadoo dot nl
7 years ago
An observation about the _use_ of array_product with primes:

$a=$arrayOfSomePrimes=(2,3,11);
              // 2 being the first prime (these days)

$codeNum=array_product($a); // gives 66 (== 2*3*11)

echo "unique product(\$a) = " . array_product($a) . "\n";

The 66 can (only) be split into its original primes,
which can be transformed into their place in the row of primes (2,3,5,7,11,13,17,19...)  giving (1,2,3,4,5,6,7,8...)

The 66 gives the places {1,2,5} in the row of primes. The number "66" is unique as a code for {1,2,5}

So you can define the combination of table-columns {1,2,5} in "66". The bigger the combination, the more efficient in memory/transmission, the less in calculation.
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