PHP - Update Query Not Working Properly

case "update-delete":
	if(isset($_POST['highlight-purchased'])) 
		{
			// ****** Setup customized query to obtain only items that are checked ******
			$sql = "SELECT * FROM shoplist WHERE";
					for($i=0; $i < count($_POST['checkboxes']); $i++)
						{
							$sql=$sql . " idnumber=" . $_POST['checkboxes'][$i] . " or";
						}
					$sql= rtrim($sql, "or");
											
			$statement = $conn->prepare($sql);
			$statement->execute();
																						
			// *** fetch results for all checked items (1st query) *** //
			$result = $statement->fetchAll();

			$statement->closeCursor();
											
			// Setup query that will change the purchased flag to "N", if it's currently set to "Y"
			$sqlSetToN = "UPDATE shoplist SET purchased = 'N' WHERE purchased = 'Y'";
											
			// Setup query that will change the purchased flag to "Y", if it's currently set to "N", "", or NULL
			$sqlSetToY = "UPDATE shoplist SET purchased = 'Y' WHERE purchased = 'N' OR purchased = '' OR purchased IS NULL";

			$statementSetToN = $conn->prepare($sqlSetToN);
			$statementSetToY = $conn->prepare($sqlSetToY);
											
			/*** loop through the results/collection of checked items ***/
			foreach($result as $row)
				{
					if ($row["purchased"] != "Y")
						{
							// *** fetch one row at a time pertaining to the 2nd query *** //
							$resultSetToY = $statementSetToY->fetch();
															
							foreach($resultSetToY as $row)
								{															
									$statementSetToY->execute();																
								}
						}
					else
						{
							// *** fetch one row at a time pertaining to the 2nd query *** //
							$resultSetToN = $statementSetToN->fetch();
															
							foreach($resultSetToN as $row)
								{															
									$statementSetToN->execute();																
								}
						}
				}
				break;
		}

$query = "SELECT * FROM ttn01 WHERE id = $_GET['id']";

Before : http://www.example.com/?a=3&id=5&start=0
After : http://www.example.com/?a=3

Before : http://www.example.com/?id=5&start=0
After : http://www.example.com/

Before : http://www.example.com/?alpha=1&id=5&start=0&beta=2
After : http://www.example.com/?alpha=1&beta=2

if ($searchtype == "store_name")
   {
       $sql = "SELECT * FROM `shoplist` WHERE store_name LIKE :searchterm ORDER BY store_name ASC";
   }
else if ($searchtype == "item_description")
   {
       $sql = "SELECT * FROM `shoplist` WHERE item_description LIKE :searchterm ORDER BY store_name ASC";
   }

// Tried this first but it didn't work...gave some kind of error pertaining to the parameter 2    
// Prepare the query ONCE
$query = "SELECT * FROM `shoplist` WHERE ? LIKE ? ORDER BY ? ASC";

$searchterm = '%' . $searchterm . '%';

$statement = $conn->prepare($query);
$statement->bindValue(1, $searchtype);                                                        
$statement->bindParam(2, $searchterm);
$statement->bindValue(3, $searchtype);
$statement->execute();

// ----------------------------------------------------------------------------------------------------------- //

// Tried this as well, but was getting unexpected results (mostly all rows being returned, regardless of input)
// Prepare the query ONCE
$query = "SELECT * FROM `shoplist` WHERE :searchtype LIKE :searchterm ORDER BY :searchtype ASC";

$searchterm = '%' . $searchterm . '%';

$statement = $conn->prepare($query);
$statement->bindValue(':searchtype', $searchtype);
$statement->bindValue(':searchterm', '%' . $searchterm . '%');
$statement->execute();

// create short variable names
if(isset($_POST['searchtype']))
    {                                            
        $searchtype=$_POST['searchtype'];
    }
if(isset($_POST['searchterm']))
    {                            
        $searchterm=trim($_POST['searchterm']);
    }

if(isset($_POST['searchtype']) && isset($_POST['searchterm']))
    {
        if (!get_magic_quotes_gpc())
            {
                $searchtype = addslashes($searchtype);
                $searchterm = addslashes($searchterm);
            }
    }

if(isset($_POST['searchtype']) && isset($_POST['searchterm']))
    {
        // ****** Setup customized query ******
        if ($searchtype == "store_name")
            {
                // The following statement is potentially open to SQL-inection attack and has therefore been REM(arked)
                // $sql = "SELECT * FROM `shoplist` WHERE " . $searchtype . " LIKE :searchterm ORDER BY store_name ASC";

                // The following may not be open to SQL-injection attack, but has the column name hard-coded in-between the WHERE and LIKE clauses
                // I would like the the column name to be set based on the value chosen by the user in the form dropdown listbox for "searchtype"
                $sql = "SELECT * FROM `shoplist` WHERE store_name LIKE :searchterm ORDER BY store_name ASC";
            }
        else if ($searchtype == "item_description")
            {
                // The following statement is potentially open to SQL-inection attack and has therefore been REM(arked)
                // $sql = "SELECT * FROM `shoplist` WHERE " . $searchtype . " LIKE :searchterm ORDER BY item_description ASC";

                // The following may not be open to SQL-injection attack, but has the column name hard-coded in-between the WHERE and LIKE clauses
                // I would like the the column name to be set based on the value chosen by the user in the form dropdown listbox for "searchtype"
                $sql = "SELECT * FROM `shoplist` WHERE item_description LIKE :searchterm ORDER BY item_description ASC";
            }

        $statement = $conn->prepare($sql);
        $statement->bindValue(':searchterm', '%' . $searchterm . '%');
        $statement->execute();
        ...
        ...
        ...
    }

<?php
$browsee = get_browser(null,true);
$array = (array_slice($browsee,5,-24));

if(in_array("Firefox",$array)){
echo "your browser is firefox";
}else if(in_array("Chromium",$array)){
echo "your browser is chromium";
}else if(in_array("Chrome",$array)){
echo "your browser is chrome";
}else if(in_array("Explorer",$array)){
echo "your browser is Internet Explorer";
}else{
echo "your browser was not detected";
}
echo '<br>';
echo '<br>';
print_r($browsee);
?>