array_product

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

array_product — 计算数组中所有值的乘积

说明

array_product(array $array): int|float

array_product() 以整数或浮点数返回一个数组中所有值的乘积。

参数

array: 这个数组。

返回值

以整数或浮点数返回一个数组中所有值的乘积。

更新日志

版本	说明
8.3.0	当 `array` 值不能转换为 int 或 float 时，现在会发出 `E_WARNING`。之前会忽略 array 和 object，而其它的值会转换为 int。此外，现在也会转换定义了数字转换的对象（比如 GMP）而不是忽略它。

示例

示例 #1 array_product() 示例

<?php

$a = array(2, 4, 6, 8);
echo "product(a) = " . array_product($a) . "\n";
echo "product(array()) = " . array_product(array()) . "\n";

?>

以上示例会输出：

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

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＋添加备注

用户贡献的备注 6 notes

down

Andre D ¶

18 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.

down

bsr dot anwar at gmail dot com ¶

7 years ago

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

down

gergely dot lukacsy at streamnet dot hu ¶

1 year ago

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);

?>

down

biziclop ¶

2 years ago

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
?>

down

Marcel G ¶

14 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;

}

?>

down

-5

Jimmy PHP ¶

10 years 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)