Comparing missing numbers in an array. PHP - php

Question

I got this script which looks up taken times in this table and then removes those times from these three arrays. The arrays are times 1-24.
The ultimate goal of this script is to compare all the missing times from these arrays and make one big array with only the available times.
The catch is it needs to check if a time is missing three times in a row. If it is, that time will not display in the final array.
For example:
<?php
include 'db-connect.php';
if (isset($_GET['month']) && isset($_GET['day']) && isset($_GET['year'])) {
$month = $_GET['month'];
$day = $_GET['day'];
$year = $_GET['year'];
//string together date
$date = $month."/".$day."/".$year;
//define the queries
$sql1 = mysql_query("SELECT start_time, server FROM classes WHERE date = '$date' AND server = '1'");
$sql2 = mysql_query("SELECT start_time, server FROM classes WHERE date = '$date' AND server = '2'");
$sql3 = mysql_query("SELECT start_time, server FROM classes WHERE date = '$date' AND server = '3'");
//define time lists for each server
$timelist1 = range(1, 24);
$timelist2 = range(1, 24);
$timelist3 = range(1, 24);
//unset the arrays with the taken times for server 1
while($query1 = mysql_fetch_array($sql1)) {
unset($timelist1[$query1['start_time'] - 1]);
}
//unset the arrays with the taken times for server 2
while($query2 = mysql_fetch_array($sql2)) {
unset($timelist2[$query2['start_time'] - 1]);
}
//unset the arrays with the taken times for server 3
while($query3 = mysql_fetch_array($sql3)) {
unset($timelist3[$query3['start_time'] - 1]);
}
//now see which times are missing three times in a row and make one final array of available times.
//code goes here...
}
?>

Answer 1

Instead of your current strategy you could just store the number of arrays each time is found in, like:
include 'db-connect.php';
if (isset($_GET['month']) && isset($_GET['day']) && isset($_GET['year'])) {
$month = $_GET['month'];
$day = $_GET['day'];
$year = $_GET['year'];
//string together date
$date = $month."/".$day."/".$year;
//define time list
$timelist = array_fill(1, 24, 0);
while($query1 = mysql_fetch_array($sql1)) {
$timelist[$query1['start_time']]++;
}
while($query2 = mysql_fetch_array($sql2)) {
$timelist[$query2['start_time']]++;
}
while($query3 = mysql_fetch_array($sql3)) {
$timelist[$query3['start_time']]++;
}
$timelist = array_keys(array_filter($timelist, 'equals3'));
function equals3($x){
return $x == 3;
}
Now $timelist is an array of times that were found in all three queries. If you want an array of times that were missing from at least one query use this instead of the last few lines:
$timelist = array_keys(array_filter($timelist, 'lessThan3'));
function lessThan3($x){
return $x < 3;
}
Edit for variable amount of servers.
// Here you can list the servers you want to include in the query
// In an array form so it can be filled easily
$servers = array(1,2,4,5);
$num_servers = count($servers);
// Convert servers into queryable format
$servers = '(\''.implode('\',\'', $servers).'\')';
$query = 'SELECT `start_time`, COUNT(*) as `count` FROM `classes`
WHERE `date` = \''.$date.'\' AND `server` IN '.$servers.'
GROUP BY `start_time`';
$result = mysql_query($query);
$timelist = array_fill(1, 24, 1);
while($row = mysql_fetch_row($result))
if($row[1] == $num_servers) // `start_time` is missing from at least one server
unset($timelist[$row[0]]);
$timelist = array_keys($timelist);
// Now $timelist is an array of times that are available on at least one server from the query
Please note that since your date variable comes from $_GET you should be very careful of MySQL Injection attacks. Someone could delete your whole database, or worse, if you don't have the right protection in place. Please read this: http://www.learnphponline.com/security/sql-injection-prevention-mysql-php