1) Copy this gist to project/console/controllers. 2) call -- yii reverse/migrate > tmp.migrate.php 3) copy functions to existing migration class.

ReverseController.php

<?php
namespace console\controllers;
use \Yii;
class ReverseController extends \yii\console\Controller
{

    public function actionMigrate() {
        // $schema = $args[0];
        $tables = Yii::$app->db->schema->getTableSchemas();

        $addForeignKeys = '';
        $dropForeignKeys = '';

        $result = "<?php\npublic function safeUp()\n{\n";
        foreach ($tables as $table) {
            $compositePrimaryKeyCols = array();

            // Create table
            $result .= '    $this->createTable(\'' . $table->name . '\', array(' . "\n";
            foreach ($table->columns as $col) {
                $result .= '        \'' . $col->name . '\' => ' . $this->getColType($col) . ',' . "\n";

                if ($col->isPrimaryKey && !$col->autoIncrement) {
                    // Add column to composite primary key array
                    $compositePrimaryKeyCols[] = $col->name;
                }
            }
            $result .= '    ), \'\');' . "\n\n";

            // Add foreign key(s) and create indexes
            foreach ($table->foreignKeys as $col => $fk) {
                // Foreign key naming convention: fk_table_foreignTable_col (max 64 characters)
                $refColumn = end($fk);
                $column = key($fk);
                $fkName = substr('fk_' . $table->name . '_' . $fk[0] . '_' . $column, 0 , 64);
                $addForeignKeys .= '    $this->addForeignKey(' . "'$fkName', '$table->name', '$column', '$fk[0]', '$refColumn', 'NO ACTION', 'NO ACTION');\n\n";
                $dropForeignKeys .= '    $this->dropForeignKey(' . "'$fkName', '$table->name');\n\n";

                // Index naming convention: idx_col
                $result .= '    $this->createIndex(\'idx_' . $column . "', '$table->name', '$column', FALSE);\n\n";
            }

            // Add composite primary key for join tables
            if ($compositePrimaryKeyCols) {
                $result .= '    $this->addPrimaryKey(\'pk_' . $table->name . "', '$table->name', '" . implode(',', $compositePrimaryKeyCols) . "');\n\n";

            }

        }
        $result .= $addForeignKeys; // This needs to come after all of the tables have been created.
        $result .= "}\n\n\n";

        $result .= "public function safeDown()\n{\n";
        $result .= $dropForeignKeys; // This needs to come before the tables are dropped.
        foreach ($tables as $table) {
            $result .= '    $this->dropTable(\'' . $table->name . '\');' . "\n";
        }
        $result .= "}\n";


        echo $result;

        return self::EXIT_CODE_NORMAL;
    }

    public function getColType($col) {
        if ($col->isPrimaryKey && $col->autoIncrement) {
            return "Schema::TYPE_PK";
        }
        $type = 'Schema::TYPE_'.strtoupper($col->type).' . \'';
        $typeSize = $col->size ? "({$col->size})" : "";
        $result = $type.$typeSize;
        if (!$col->allowNull) {
            $result .= ' NOT NULL';
        }
        if ($col->defaultValue != null) {
            $result .= " DEFAULT {$col->defaultValue}";
        } elseif ($col->allowNull) {
            $result .= ' DEFAULT NULL';
        }
        return $result.'\'';
    }
}