Array Rand Not Working with MySQL Fetch Array - php

Question

I wrote a PHP script that retrieves values from a MySQL Query. I used mysql_fetch_array to add the results to an array. I am trying to select a random value from the array, however array_rand doesn't seem to work. My code is below:
<?php
session_start();
ob_start();
require_once 'includes/db_connection.php';
require_once 'includes/contest.php';
require_once 'includes/survey.php';
require_once 'includes/poll.php';
require_once 'includes/clients.php';
require_once 'includes/user.php';
//Select All Entries from Contest and Save as Array
//Select
mysql_connect(localhost,s2ktest_s2kuser, Bc33iyZYQWgUmguBehPI);
$dbname = 's2ktest_s2k';
mysql_select_db($dbname);
$contestid = 20;
$query = "SELECT UserID FROM Contest_Entered WHERE ContestID = $contestid";
//Save Result
$result = mysql_query($query) or die(mysql_error());
//Save All Contest Entries in Array
$entries = mysql_fetch_array($result) or die(mysql_error());
//Output all Rows
//While Each Entry in the Array is a Value
while($entries = mysql_fetch_array($result))
{
echo $entries;
echo "</br>";
}
echo array_rand($entries);
//mysql_free_result($result);
?>

Answer 1

Maybe because you don't have any array...
The while is only generating one row at the time.
while($entries = mysql_fetch_array($result))
{
echo $entries;
$arr[] = $entries;
echo "</br>";
}
echo array_rand($arr);

Answer 2

mysql_fetch_array() retrieves only one row at a time. First, load the whole result set into an array using the [] append syntax, then fetch randomly from that.
$all_entries = array();
// Using MYSQL_NUM to retrieve only numeric keys
// by default, mysql_fetch_array() gets both numeric and associative keys
while($entries = mysql_fetch_array($result, MYSQL_NUM))
{
// Append all rows onto an array, only a sinlge value so you get a 1D array
$all_entries[] = $entries[0];
}
// Then call array_rand() against $all_entries
echo array_rand($all_entries);
Disclaimer:
Start thinking about migrating away from the old mysql_*() functions to a modern API supporting prepared statements. PDO is excellent and portable between RDBMS, while MySQLi is a good alternative as well.

Answer 3

That's because you're changing the value of $entries from an array to a string when you start the loop. Try echoing array_rand($entries) before the loop instead.
However, if you are instead trying to retrieve a random row from a table (rather than a random column from a row, as your code appears to do) use ORDER BY RAND() in your query. It's unclear what you're going for.
Good luck!