SELECT * FROM (tablename) WHERE (array values) = '1' - php

Question

I have this question about SQL queries.
Here its is:
$allowed = array("Amsterdam", "Arnhem", "Assen", "Groningen", "Leeuwarden", "Rotterdam", "Sittard", "Tilburg", "Utrecht");
$filter = $db->prepare("SELECT * FROM users WHERE '$allowed' = '1'");
$filter->execute;
foreach($filter->fetchAll(PDO::FETCH_OBJ) as $filtered):
$amsterdam = $filtered->amsterdam;
$arnhem = $filtered->arnhem;
$assen = $filtered->assen;
$groningen = $filtered->groningen;
$leeuwarden = $filtered->leeuwarden;
$rotterdam = $filtered->rotterdam;
$sittard = $filtered->sittard;
$utrecht = $filtered->utrecht;
endforeach;
The output (when echoed) is blank.
How can I get the query to look for column names from the array?
All help is appreciated.

Answer 1

This did it for me:
$query = $db->prepare("SELECT * FROM tbl_users WHERE id = '{$userId}'");
$query->execute();
foreach($query->fetchAll(PDO::FETCH_OBJ) as $value){
$districts = array("amsterdam","arnhem","assen","groningen","leeuwarden","rotterdam","sittard","tilburg","utrecht","antillen","missie","dap","sap");
$arrlength = count($districts);
for($x = 0; $x < $arrlength; $x++) {
if($value->$districts[$x] == TRUE){
echo '<pre>';
echo ucfirst($districts[$x]) . ' --> ' . $value->$districts[$x];
echo '</pre>';
}
}
}