Here's one way you might do it:
function run_query($query)
{
$out = '';
$db = new PDO("mysql:host=localhost;dbname=test","test","test");
$out = $db->query($query)->fetchAll();
return $out;
}
$results = run_query('SHOW TABLES');
$tables = array();
foreach($results as $result)
$tables[] = $result['Tables in test']; // Note, replace "test" with your database name
$temp = implode(',', $tables);