array_product

(PHP 5 >= 5.1.0, PHP 7)

array_product — 计算数组中所有值的乘积

说明

number array_product ( array $array )

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

Example #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

用户评论:

[#1] Jimmy PHP [2014-04-29 19:55:14]

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)

[#2] Marcel G [2010-09-28 08:36:54]

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; } ?>

[#3] pqpqpq at wanadoo dot nl [2007-01-17 04:32:43]

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.

[#4] Andre D [2006-08-07 13:56:19]

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.