问时间数组查找比设置时间早15分钟的时间

EN

session_start();
date_default_timezone_set('America/Chicago');

error_reporting(E_ALL);
include 'DB.php';

$timestamp = time();

echo 'Timestamp:';
echo $timestamp;
echo '------';

$drop_dead = mysql_query("SELECT due_date, ID FROM eblasts") or die(mysql_error());

while ($row = mysql_fetch_array($drop_dead, MYSQL_NUM)) {
        $final_email_id[$row[1]] = $row[0];
};

//this is the ID's of eblasts that need an email sent based on their drop_dead NOT on warning1, warning2 and due_date.
print_r($final_email_id);

foreach($final_email_id as $key => $value) {
 $query = mysql_query("SELECT warning_1 FROM eblasts WHERE ID = '$key'") or die(mysql_error());
 $find_warning_1 = mysql_fetch_row($query);
 $warning_1[$key] = $find_warning_1[0];
}
//this is the warning_1 numbers where the ID's of the array are the ID's of the eblast.
print_r($warning_1);

foreach($final_email_id as $key => $value) {
 $query = mysql_query("SELECT warning_2 FROM eblasts WHERE ID = '$key'") or die(mysql_error());
 $find_warning_2 = mysql_fetch_row($query);
 $warning_2[$key] = $find_warning_2[0];
}

//this is the warning_2 numbers where the ID's of the array are the ID's of the eblast.
print_r($warning_2);

foreach($final_email_id as $key => $value) {
 $query = mysql_query("SELECT due_date FROM eblasts WHERE ID = '$key'") or die(mysql_error());
 $find_due_date = mysql_fetch_row($query);
 $due_date[$key] = $find_due_date[0];
}

//this is the due date numbers where the ID's of the array are the ID's of the eblast.
print_r($due_date);

//Add 900 because its 15 minutes in seconds ... 
$run_time = $timestamp + 900;

foreach($warning_1 as $key => $value){
 $diff_time = $run_time - $warning_1[$key];
 echo '-----';
 echo $diff_time;
 echo '-----';
 if($diff_time < 900 && $diff_time > 0){
 echo 'different';
 echo $diff_time;
 $_SESSION['eblast_id'] = $key;
 include 'warning_1.php'; 
 }
};