yii\db\sqlite\Schema::findConstraints PHP Method

    protected function findConstraints($table)
    {
        $sql = 'PRAGMA foreign_key_list(' . $this->quoteSimpleTableName($table->name) . ')';
        $keys = $this->db->createCommand($sql)->queryAll();
        foreach ($keys as $key) {
            $id = (int) $key['id'];
            if (!isset($table->foreignKeys[$id])) {
                $table->foreignKeys[$id] = [$key['table'], $key['from'] => $key['to']];
            } else {
                // composite FK
                $table->foreignKeys[$id][$key['from']] = $key['to'];
            }
        }
    }