Getting a value from a database and echoing from another file - php

Question

I am trying to Select a row from a database table and display the variables in another PHP file. Right now I have to trying just one variable, but will change to outputting a table later on. The error is an Undefined Variable:output.
I have tried using session but it prints out the array and doesn't go all the way through. I really just want the variable so that I can put them into a table easier.
My store file, which shows a search bar and where I am trying to display the results, under the search bar.
<?php
require "header.php";
?>
<main>
<form action="includes/itemsearch.php" method="get">
Please enter the Item you are looking for:<br>
<input type="text" name="item" placeholder="Search for an item...">
<br><br>
<button type="submit" name="search-submit">Search</button>
</form>
<?php echo $output ?>
</main>
<?php
require "footer.php";
?>
My item search file:
<?php
if (isset($_GET['search-submit'])) {
require 'connect.php';
$item = $_GET['item'];
$output = "";
$sql = "SELECT * FROM Product";
$result=mysqli_query($conn,$sql);
while($row=mysqli_fetch_array($result)){
$pName =$row['Product_Name'];
$manufacture=$row['Manufacture'];
$quantity=$row['Quantity'];
$price=$row['Price'];
$description=$row['Description'];
echo"<p>$pName</p><br />";
}
header("Location: ../store.php?");
}
I currently get an undefined variable error.

Answer 1

use post method instead of get
<?php
if (isset($_POST['search-submit'])) {
}
?>

Answer 2

$output is undefined because you initialize it on click of submit button so <?php echo $output ?> is executing first then it gets initialized.
try
<?php
if (isset($_GET['search-submit'])){
echo $output;
}
?>
to get output just require search file in store.php
// store.php
<?php
require "header.php";
require "search.php";
?>
<main>
<form action="" method="get">
Please enter the Item you are looking for:<br>
<input type="text" name="item" placeholder="Search for an item...">
<br><br>
<button type="submit" name="search-submit">Search</button>
</form>
<?php echo $output ?>
</main>
<?php
require "footer.php";
?>
this is the final code
// search.php
<?php
if (isset($_GET['search-submit'])) {
require 'connect.php';
$item = $_GET['item'];
$output = "";
$sql = "SELECT * FROM Product";
$result=mysqli_query($conn,$sql);
while($row=mysqli_fetch_array($result)){
$pName =$row['Product_Name'];
$manufacture=$row['Manufacture'];
$quantity=$row['Quantity'];
$price=$row['Price'];
$description=$row['Description'];
$output .= "<p>$pName</p><br />";
}
}
?>
// store.php
<?php
require "header.php";
require "search.php";
?>
<main>
<form action="" method="get">
Please enter the Item you are looking for:<br>
<input type="text" name="item" placeholder="Search for an item...">
<br><br>
<button type="submit" name="search-submit">Search</button>
</form>
<?php echo isset($_GET['search-submit']) ? $output : '' ?>
</main>
<?php
require "footer.php";
?>