Retrieve data using checkboxes php mysql

[Martha Van Orshoven]

here is the php code:
// Connect to the database
require_once('connectvars.php');
$dbc = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME, DB_PORT, DB_PATH);
// Error checks
//if no categories are checked - report an error to the user

// New Query to get the results
$query = "SELECT * FROM common_name, main_native WHERE"

// open the parens in the query to start the category OR clause
$query = $query ."( "
if (category[grass].checked) THEN
$query = $query . "( main_native.category = "grass" ) OR"
end if

if (category[tree].checked THEN
$query = $query . "( main_native.category = "tree" ) OR "
end if

if (category[wildflowers & herbs].checked THEN
$query = $query . "( main_native.category = "wildflowers & herbs" ) OR "
end if

if (category[shrubs & vines].checked THEN
$query = $query . "( main_native.category = "shrubs & vines" ) OR "
end if
// we have an extra " OR " at the end of the query that want to remove
//$query = $query - trailing " OR "

// close paren from category OR clause -
// $query = $query . ") "
. ") "

The code is crashing on the first line. I'm pretty new and don't know where I'm going wrong.