Storing database value into variable - php

Question

My table category has these columns:
idcategory
categorySubject
users_idusers
I have a form with a simple radio buttons and a textbox.
I have a select all statement for category and need to get the idcategory stored into a variable ($getCatId) so I can use this statement:
$sql="INSERT INTO topic(subject, topicDate, users_idusers, category_idcategory, category_users_idusers) VALUES('($_POST[topic])', '$date', '$_SESSION[userid]', '$getCatId', '$_SESSION[userid]');";
What is the best way to get and store categoryid?
if($_SERVER['REQUEST_METHOD'] != 'POST') //show form if not posted
{
$sql = "SELECT * FROM category;";
$result = mysqli_query($conn,$sql);
?>
<form method="post" action="createTopic.php">
Choose a category:
</br>
</br>
<?php
while ($row = mysqli_fetch_assoc($result)) {
echo "<div class= 'choice'><input type='radio' name='category' value='". $row['idcategory'] . "'>" . $row['categorySubject'] ."</div></br>";
}
echo 'Topic: <input type="text" name="topic" minlength="3" required>
</br></br>
<input type="submit" value="Add Topic" required>
</form>';
}
if ($_POST){
if(!isset($_SESSION['signedIn']) && $_SESSION['signedIn'] == false)
{
echo 'You must be signed in to contribute';
}
else{
$sql="INSERT INTO topic(subject, topicDate, users_idusers, category_idcategory, category_users_idusers) VALUES('($_POST[topic])', '$date', '$_SESSION[userid]', '$getCatId', '$_SESSION[userid]');";
$result = mysqli_query($conn,$sql);
echo "Added!";

Answer 1

If I understand this question correctly, you'll have your $getCatId (id of the category) in $_POST['category'] (after sending form) in your case

Answer 2

The first thing you should do is protect yourself from SQL injection by parameterizing your queries before old Bobby Tables comes to pay you a visit.
You might also look into using PDO as I've demonstrated below because it's a consistent API that works with a lot of different database management systems, so this leads to wonderfully portable code for you. Here's an annotated working example on Github:
<?php
// returns an intance of PDO
// https://github.com/jpuck/qdbp
$pdo = require __DIR__.'/mei_DV59j8_A.pdo.php';
// dummy signin
session_start();
$_SESSION['signedIn'] = true;
$_SESSION['userid'] = 42;
//show form if not posted
if($_SERVER['REQUEST_METHOD'] != 'POST'){
$sql = "SELECT * FROM category;";
// run query
$result = $pdo->query($sql);
?>
<form method="post" action="createTopic.php">
Choose a category:
</br>
</br>
<?php
// get results
while ($row = $result->fetch(PDO::FETCH_ASSOC)) {
echo "
<div class= 'choice'>
<input type='radio' name='category' value='$row[idcategory]'/>
$row[categorySubject]
</div>
</br>
";
}
echo '
Topic: <input type="text" name="topic" minlength="3" required>
</br></br>
<input type="submit" value="Add Topic" required>
</form>
';
}
if ($_POST){
if(!isset($_SESSION['signedIn']) && $_SESSION['signedIn'] == false){
echo 'You must be signed in to contribute';
} else {
// simulate your date input
$date = date("Y-m-d");
// bind parameters
$sql = "
INSERT INTO topic (
subject, topicDate, users_idusers, category_idcategory, category_users_idusers
) VALUES(
:subject, :topicDate, :users_idusers, :category_idcategory, :category_users_idusers
);
";
// prepare and execute
$statement = $pdo->prepare($sql);
$statement->execute([
'subject' => "($_POST[topic])",
'topicDate' => $date,
'users_idusers' => $_SESSION['userid'],
// to answer your question, here's your variable
'category_idcategory' => $_POST['category'],
'category_users_idusers' => $_SESSION['userid'],
]);
echo "Added!";
}
}