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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。

    示例

    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";

    ?>

    以上示例会输出：

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

    ＋add a note

    User Contributed Notes 7 notes

    up
    26
    Andre D
    17 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
    10
    bsr dot anwar at gmail dot com
    6 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
    up
    -1
    biziclop
    1 year 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
    ?>
    up
    -1
    Marcel G
    13 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
    -4
    Jimmy PHP
    9 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)
    up
    -1
    gergely dot lukacsy at streamnet dot hu
    7 months 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);

    ?>
    up
    -8
    pqpqpq at wanadoo dot nl
    16 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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