PHP 的 array_rand() 不是真正随机的？

Question

我正在编写一些代码来随机化演示文稿列表。同一演示文稿无法连续播放。

$d 数组将是演示文稿 ID 的列表以及演示文稿应循环播放的次数。

下面的代码工作正常，但结果并不是真正随机的。当我开始一遍又一遍地看到相同的模式时，我正在调试。看看这个输出:

ighbajafpbailgjacbiaeldiqjaphafgdjcbapsaebjfdkcknijhbdgecaimabodalkfbgbhacbhnrjeofbdjbfhegmbpdkialmbocnliaebfaimcabchgoecbcdimgepnfjgfbfbohdahdkjgneaebha

ighbajafpbailgjacbiaeldiqjaphafgdjcbapsaebjfdkcknijhbdgecaimabodalkfbgbhacbhnrjeofbdjbfhegmbpdkialmbocnliaebfaimcabchgoecbcdimgepnfjgfbfbohdahdkjgneaebha

这两个相差 4 分。它们是相同的。 4 运行后，相同的相同字符串。再运行 4 次，相同的字符串。事实上，当我运行它时，我似乎按顺序得到了相同的 4 个字符串。

我的代码在下面，谁能指出我可能犯了什么错误？如果我什么都没做，为什么“rand”不是随机的？我该如何解决这个问题？

$d = array(
    array('a', '20'), array('b', '20'), array('c', '10'), array('d', '10'), array('e', '10'), array('f', '10'), array('g', '10'), array('h', '10'), array('i', '10'), array('j', '10'), array('k', '5'), array('l', '5'), array('m', '5'), array('n', '5'), array('o', '5'), array('p', '5'), array('q', '1'), array('r', '1'), array('s', '1'));
$out = randomizeArray($d);
//var_dump($out);

function randomizeArray ($data) {
    // Step 1: Make an array of the id's with repeats for count.
    $rarray = array();
    foreach ($data as $i => $v) {
        while ($data[$i][1] > 0) {
            array_push($rarray, $data[$i][0]);
            $data[$i][1]--;
        }
    }
    // Step 2: Randomize.
    $stat = 1;
    while ($stat == '1') {
        //echo "<br><br>Randomizing Array: <br>";
        $stat = rarr($rarray);
    }
    return $stat;
}
function rarr ($a) {
    $r = array();
    $last = "";
    while ($a) {
        $rand = array_rand($a, 1);
        // Does this value match the last one we got?
        if ($a[$rand] != $last) {
            // Nope. Transfer to our $r array.
            echo $a[$rand];
            array_push($r, $a[$rand]);
            $last = $a[$rand];
            unset($a[$rand]);
        } else {
            // We have a match between our "last" presentation and the one we just selected.
            // We need to scan our array and verify that we still have different values.
            $check = $a[$rand];
            foreach ($a as $c) {
                if ($check != $c) {
                    // We have at least 2 different values in our array still.
                    // Rerun the while loop
                    continue 2;
                }
            }
            // All of the values left in our array are repeats.
            // That's no good, so return an error and rerun.
            return 1;
        }
    }
    // Everything is awesome. Return the randomized array.
    return $r;
}

Answer 1

据我所知，解决方案是在第 2 步之前添加行:

shuffle($rarray);

看来问题有点解决了。重复精确到 47 次。

如果相反，您在 rarr 函数中的 while 之后添加它:

while ($a) {
    shuffle($a);

if 会重复 52 次

看来这实际上是 array_rand 函数的问题。在下面的代码中将 array_rand 更改为 mt_rand:

<?php
$d = array(
    array('a', '20'), array('b', '20'), array('c', '10'), array('d', '10'), array('e', '10'), array('f', '10'), array('g', '10'), array('h', '10'), array('i', '10'), array('j', '10'), array('k', '5'), array('l', '5'), array('m', '5'), array('n', '5'), array('o', '5'), array('p', '5'), array('q', '1'), array('r', '1'), array('s', '1'));

    for ($i=0; $i<10000; ++$i) {
        //ho "x";
        $out = randomizeArray($d);
        echo implode('',$out)."<br />";   
    }    


//var_dump($out);

function randomizeArray ($data) {
    // Step 1: Make an array of the id's with repeats for count.
    $rarray = array();
    foreach ($data as $i => $v) {
        while ($data[$i][1] > 0) {
            array_push($rarray, $data[$i][0]);
            $data[$i][1]--;
        }
    }
    // Step 2: Randomize.
    $stat = 1;
    while ($stat == '1') {
        //echo "<br><br>Randomizing Array: <br>";
        $stat = rarr($rarray);
    }
    return $stat;
}
function rarr ($a) {
    $r = array();
    $last = "";
    while ($a) {
        $rand = mt_rand(0,count($a)-1);
        // Does this value match the last one we got?
        if ($a[$rand] != $last) {
            // Nope. Transfer to our $r array.
           // echo $a[$rand];
            array_push($r, $a[$rand]);
            $last = $a[$rand];
            unset($a[$rand]);
            $a = array_values($a);
        } else {
            // We have a match between our "last" presentation and the one we just selected.
            // We need to scan our array and verify that we still have different values.
            $check = $a[$rand];
            foreach ($a as $c) {
                if ($check != $c) {
                    // We have at least 2 different values in our array still.
                    // Rerun the while loop
                    continue 2;
                }
            }
            // All of the values left in our array are repeats.
            // That's no good, so return an error and rerun.
            return 1;
        }
    }
    // Everything is awesome. Return the randomized array.
    return $r;
}

使字符串真正独一无二。

我真的很好奇是否有人可以解释这是一个 PHP 错误或“功能”