Determine table existence
SELECT * FROM table WHERE FALSE;

SELECT * FROM table WHERE 0;

SELECT * FROM table WHERE column = false;

if there's table `table`
    return 0 rows (minimal database overhead) and valid resource
else
    return false

SELECT count(*)
FROM information_schema.tables
WHERE table_schema = <schema-or-db-name>
AND table_name = <table-or-view-name>

$sql="SELECT * FROM $table";
$result=mysql_query($sql);
if (!$result)
{
// table does not exist
}

$sql="SELECT * FROM $table where user_id = 1";