PHP SQL query doesnt return a result - php

Question

I have a button in a webapp that allows users to request a specially formatted number. When a user click this button 2 scripts run. The first that is fully functional, looks at a number table finds the largest number and increments it by 1. (This is not the Primary Key) the second script which is partially working gets the current date and runs a SQL query to get which period that date falls in. (Periods in this case not always equaling a full month) I know this script is at least partially working because I can access the $datetoday variable called in that script file. However it is not returning the requested data from the periods table. Anyone that could help me identify what I am doing wrong?
<?php
include 'dbh.inc.php';
$datetoday = date("Ymd");
$sql = "SELECT p_num FROM periods where '$datetoday' BETWEEN p_start AND p_end";
$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)) {
header("Location: ../quote.php?quotes=failed_to_write");
exit();
} else {
mysqli_stmt_execute($stmt);
mysqli_stmt_store_result($stmt);
$result = mysqli_stmt_get_result($stmt);
$row = mysqli_fetch_assoc($result);
$pnum = $row;
mysqli_stmt_close($stmt);
}
If it helps any one I published my code to https://github.com/cwilson-vts/Quote-Appliction

Answer 1

So first off, I do not use msqli and never learned it. However, I believe I get the gist of what you want to do. I use PDO because I FEEL that it is easier to use, easier to read and it's also what I learned starting off. It's kinda like Apple vs. Samsung... no one product is exactly wrong or right. And each have their advantages and disadvantages. What I'm about to provide you will be in PDO form so I hope that you will be able to use this. And if you can't then no worries.
I want to first address one major thing that I saw and that is you interlacing variables directly into a mysql statement. This is not considered standard practice and is not safe due to sql injections. For reference, I would like you to read these sites:
http://php.net/manual/en/security.database.sql-injection.php
http://php.net/manual/en/pdo.prepared-statements.php
Next, I'm noticing you're using datetime as a variable name. I advise against this as this is reserved in most programming languages and can be tricky. So instead, I am going to change it something that won't be sensitive to it such as $now = "hello world data";
Also I'm not seeing where you would print the result? Or did you just not include that?
Another thing to consider: is your datetime variable the same format as what you are storing in your db? Because if not, you will return 0 results every time. Also make sure it is the right time zone too. Because that will really screw with you. And I will show you that in the code below too.
So now on to the actual code! I will be providing you with everything from the db connection code to the sql execution.
DB CONNECTION FILE:
<?php
$host = '127.0.0.1';
$user = 'root';
$pw = '';
$db = 'test'; // your db name here (replace 'test' with whatever your db name is)
try {
// this is the variable will call on later in the main file
$conn = new PDO("mysql:host=$host;dbname=$db;", $user, $pw);
} catch (PDOException $e) {
// kills the page and returns mysql error
die("Connection failed: " . $e->getMessage());
}
?>
The data file:
<?php
// calls on the db connection file
require 'dbconfig.php';
// set default date (can be whatever you need compared to your web server's timezone). For this example we will assume the web server is operating on EST.
date_default_timezone('US/Eastern');
$now = date("Ymd");
// check that the $now var is set
if(isset($now)) {
$query = $conn->prepare("SELECT p_num FROM periods WHERE p_start BETWEEN p_start AND :now AND p_end BETWEEN p_end AND :now");
$query->bindValue(':now', $now);
if($query->execute()) {
$data = $query->fetchAll(PDO::FETCH_ASSOC);
print_r($data); // checking that data is successfully being retrieved (only a troubleshooting method...you would remove this once you confirm it works)
} else {
// redirect as needed and print a user message
die("Something went wrong!");
}
$query->closeCursor();
}
?>
Another thing I want to mention is that make sure you follow due process with troubleshooting. If it's not working and I'm not getting any errors, I usually start at the querying level first. I check to make sure my query is executing properly. To do that, I go into my db and execute it manually. If that's working, then I want to check that I am actually receiving a value to the variable I'm declaring. As you can see, I check to make sure the $now variable is set. If it's not, that block of code won't even run. PHP can be rather tricky and finicky about this so make sure you check that. If you aren't sure what the variable is being set too, echo or print it with simply doing echo $now
If you have further questions please let me know. I hope this helps you!

Answer 2

I think I know what I was doing wrong, somebody with more PHP smarts than me will have to say for sure. In my above code I was using mysqli_stmt_store_result I believe that was clearing my variable before I intended. I changed that and reworked my query to be more simple.
<?php
include 'dbh.inc.php';
$datetoday = date("Ymd");
$sql = "SELECT p_num FROM periods WHERE p_start <= $datetoday order by p_num desc limit 1";
$stmt = mysqli_stmt_init($conn);
if(!mysqli_stmt_prepare($stmt, $sql)) {
header("Location: ../quote.php?quotes=failed_to_write");
exit();
} else {
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);
while( $row = mysqli_fetch_assoc($result)) {
$pnum = $row['p_num'];
echo $pnum;
}
mysqli_stmt_close($stmt);
}
Thanks to #rhuntington and #nick for trying to help. Sorry I am such an idiot.