array_rand函数有时会返回空

I want to make a little service.The service's main idea is to show one record from mysql table and it makes this per click at randomly.

Here is the code that i wrote:

<?php
require'connection.php';

$dbQueryFirst = $nesnePDO->prepare("SELECT CategoryID FROM Categories");
$dbQueryFirst->execute();   
while ($resultsFirst = $dbQueryFirst->fetch(PDO::FETCH_ASSOC)) 
{
    $getidFirst[] = $resultsFirst;
    $puppet = array_rand($getidFirst);
    if ($puppet == null && empty($puppet)) 
    {
        shuffle($getidFirst);       
    }       
}

$rndID = $puppet;

$dbQuerySecond = $nesnePDO->prepare("SELECT * FROM Categories WHERE CategoryID = :CategoryID");
$dbQuerySecond->bindParam(":CategoryID",$rndID);
$dbQuerySecond->execute();
$resultsSecond = $dbQuerySecond->fetchAll(PDO::FETCH_ASSOC);
echo json_encode($resultsSecond);
?>

First query is,get id's from db and take them into array.Second query,get the random id from the previous query's result and show the entire row of relevant id.And I got stuck at random function. If I need to explain this work with percentage for to be more clearly,

• Works well and get results %70
• get empty %20
• get null array [] %10

I wanted the show the screenshots but system didn't give the permission because of my reputation.So,the final statement as usual,"I'm not so good at PHP.Any idea?" Honestly,any help would be appreciated.

Your should wait for array to get filled inside your while loop and then get random value from it.

while ($resultsFirst = $dbQueryFirst->fetch(PDO::FETCH_ASSOC)) 
{
    $getidFirst[] = $resultsFirst;     
}

$puppet = array_rand($getidFirst);
$rndID = $getidFirst[$puppet];

Also, you can get random entry directly from your database without using php.

$dbQueryFirst = $nesnePDO->prepare("SELECT CategoryID FROM Categories ORDER BY RAND() LIMIT 1");
$dbQueryFirst->execute();  
$rndID = $dbQueryFirst->fetch(PDO::FETCH_ASSOC)

By the way, you should be getting your CategoryID like so

$rndID['CategoryID']

From the doc

When picking only one entry, array_rand() returns the key for a random entry

Second, $resultsFirst, i think, is array you need take item of it $resultsFirst['CategoryID']

So, use

while ($resultsFirst = $dbQueryFirst->fetch(PDO::FETCH_ASSOC))  {
    $getidFirst[] = $resultsFirst['CategoryID'];
}

$puppet = array_rand($getidFirst);
$rndID = $getidFirst[$puppet];