components/Migration.php
public function dropColumnForeignKey($table, $column)
    {
        $tableColumns = $this->db->getTableSchema($table)->columnNames;
        if (!in_array($column, $tableColumns)) {
            return;
        }
        $fks = $this->getForeignNamesColumns($this->db->getTableSchema($table));
        if ($name = array_search($column, $fks)) {
            $this->dropForeignKey($name, $table);
        }
    }
public function dropColumnForeignKey($table, $column)
    {
        $tableColumns = $this->db->getTableSchema($table)->columnNames;
        if (!in_array($column, $tableColumns)) {
            return;
        }
        $fks = $this->getForeignNamesColumns($this->db->getTableSchema($table));
        if ($name = array_search($column, $fks)) {
            $this->dropForeignKey($name, $table);
        }
    }
Удаляет внешний ключ на колонке
@param $table
@param $column