system/classes/Database.php
public function join($table, $conditions, $type = 'INNER')
    {
        $dataMember = &$this->joins;
        $item = [$table, $conditions, $type];
        array_push($dataMember, $item);
        return $this;
    }
public function join($table, $conditions, $type = 'INNER')
    {
        $dataMember = &$this->joins;
        $item = [$table, $conditions, $type];
        array_push($dataMember, $item);
        return $this;
    }
JOIN array format:
[
[
table,
[
conditions
],
type
]
]