PHP - Manual: array_product

2024-11-14

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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。

范例

示例 #1 array_product() 例子


<?php

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

?>

以上例程会输出：

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

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User Contributed Notes 5 notes

down

Andre D ¶

15 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 ¶

5 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

Marcel G ¶

11 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

-2

Jimmy PHP ¶

8 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)

down

-7

pqpqpq at wanadoo dot nl ¶

15 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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官方地址：https://www.php.net/manual/en/function.array-product.php

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array_product

说明

参数

返回值

范例

User Contributed Notes 5 notes