Update Query PHP - wiping rather than updating - php

Question

This is for an assignment, so the code is based on how the learning resources are presented. I have a plant database that I have to make changes to, and then update plantID no.2. I have created the form which is then populated with plantID 2 info, but when I click the Update button after making changes, it wipes all the info for that entry in the database. I'm not sure where I have gone wrong. Any help would be awesome.
<?php
// MySQL Database Connect
require_once("connect.php");
// read the values from the form and store in variables
$botanicName = $_POST['bot_name'];
$commonName = $_POST['comm_name'];
$plantDescription = $_POST['pl_desc'];
$commonUse = $_POST['comm_use'];
$maxHeight = $_POST['m_height'];
$maxWidth = $_POST['m_width'];
$popular = $_POST['pop'];
// escape variables for security
$botanicName = mysqli_real_escape_string($conn, $bot_name);
$commonName = mysqli_real_escape_string($conn, $comm_name);
$plantDescription = mysqli_real_escape_string($conn, $pl_desc);
$commonUse = mysqli_real_escape_string($conn, $comm_use);
$maxHeight = mysqli_real_escape_string($conn, $m_height);
$maxWidth = mysqli_real_escape_string($conn, $m_width);
$popular = mysqli_real_escape_string($conn, $pop);
// create the UPDATE query
$query="UPDATE plant SET botanicName='$botanicName', commonName='$commonName', plantDescription='$plantDescription', commonUse='$commonUse', maxHeight='$maxHeight', maxWidth='$maxWidth', popular='$popular' WHERE plantID='2'";
//execute the query
$results = mysqli_query($conn, $query );
// check for errors
if(!$results) {
echo ("Query error: " . mysqli_error($conn));
exit;
}
else {
// Redirect the browser window back to the make_changes page if there are no errors
header("location: ../make_changes.html");
}
?>
<h2>Edit a Plant</h2>
<?php
// run a select query to return the existing data for the record
$query = "SELECT * FROM plant WHERE plantID='2'";
$results = mysqli_query($conn, $query );
// capture any errors
if(!$results) {
echo ("Query error: " . mysqli_error($conn));
}
else {
// fetch and store the results for later use if no errors
while ($row = mysqli_fetch_array($results)) {
$bot_name = $row['botanicName'];
$comm_name = $row['commonName'];
$pl_desc = $row['plantDescription'];
$comm_use = $row['commonUse'];
$m_height = $row['maxHeight'];
$m_width = $row['maxWidth'];
$pop = $row['popular'];
}
}
?>
<form method="post" action="code/update_plant.php">
<p>Botanic Name: <input type="text" name="botanicName" value="<?=$bot_name?>" required></p>
<p>Common Name: <input type="text" name="commonName" value="<?=$comm_name?>"required></p>
<p>Plant Description: <input type="text" name="plantDescription" value="<?=$pl_desc?>" required></p>
<p>Common Use: <input type="text" name="commonUse" value="<?=$m_height?>" required></p>
<p>Max. Height (m): <input type="text" name="maxHeight" value="<?=$m_height?>" required></p>
<p>Max. Width (m): <input type="text" name="maxWidth" value="<?=$m_width?>" required></p>
<p>Popular? (Y/N): <input type="text" name="popular" value="<?=$pop?>"required></p>
<input type="submit" name="submit" value= "Update">
</form>

Answer 1

The parameters sent to $_POST have the name key in your input so your $_POST['bot_name'] for example is empty, the correct way to get that name is $_POST['botanicName'].
This will be your post parameters:
$botanicName = $_POST['botanicName'];
$commonName = $_POST['commonName'];
$plantDescription = $_POST['plantDescription'];
$commonUse = $_POST['commonUse'];
$maxHeight = $_POST['maxHeight'];
$maxWidth = $_POST['maxWidth'];
$popular = $_POST['popular'];

Answer 2

The names you use in the form have to exactly match the indexes you use in $_POST. You are using variables that are not defined.
// read the values from the form and store in variables
$botanicName = $_POST['botanicName'];
$commonName = $_POST['commonName'];
$plantDescription = $_POST['plantDescription'];
$commonUse = $_POST['commonUse'];
$maxHeight = $_POST['maxHeight'];
$maxWidth = $_POST['maxWidth'];
$popular = $_POST['popular'];
Fix the mysqli escape function calls:
// variable $bot_name does not exist therefore it results in a null value
$botanicName = mysqli_real_escape_string($conn, $bot_name); // bad
// Fixed
$botanicName = mysqli_real_escape_string($conn, $botanicName); // good
Make the form input names the same as $_POST
<form method="post" action="code/update_plant.php">
<p>Botanic Name: <input type="text" name="botanicName" value="<?=$botanicName?>" required></p>
<p>Common Name: <input type="text" name="commonName" value="<?=$botanicName?>"required></p>
<p>Plant Description: <input type="text" name="plantDescription" value="<?=$plantDescription?>" required></p>
<p>Common Use: <input type="text" name="commonUse" value="<?=$maxHeight?>" required></p>
<p>Max. Height (m): <input type="text" name="maxHeight" value="<?=$m_height?>" required></p>
<p>Max. Width (m): <input type="text" name="maxWidth" value="<?=$maxWidth?>" required></p>
<p>Popular? (Y/N): <input type="text" name="popular" value="<?=$popular?>"required></p>
<input type="submit" name="submit" value= "Update">
</form>

Answer 3

I needed to change the indexes in the $_POST (I was using undefined variables) and change them also in the mysqli escape functions.