Laravel migration table field's type change

Following is my file 2015_09_14_051851_create_orders_table.php. And I want to change $table->integer('category_id'); as a string with new migration.

<?php

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateOrdersTable extends Migration {

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('orders', function(Blueprint $table)
        {
            $table->increments('id');
            $table->string('num');
            $table->integer('user_id');

            $table->text('store_name');
            $table->integer('store_name_publication');

            $table->string('postal_code', 255);
            $table->string('phone_number', 255);

            $table->text('title');
            $table->text('description');

            $table->string('list_image_filename1', 255);
            $table->string('list_image_filename2', 255)->nullable();
            $table->string('list_image_filename3', 255)->nullable();
            $table->string('list_image_filename4', 255)->nullable();
            $table->string('list_image_filename5', 255)->nullable();

            $table->integer('term');

            $table->datetime('state0_at')->nullable();
            $table->datetime('state1_at')->nullable();
            $table->datetime('state2_at')->nullable();
            $table->datetime('state3_at')->nullable();
            $table->datetime('state4_at')->nullable();
            $table->datetime('state5_at')->nullable();
            $table->datetime('state6_at')->nullable();
            $table->datetime('state7_at')->nullable();
            $table->datetime('state8_at')->nullable();
            $table->datetime('state9_at')->nullable();
            $table->datetime('state10_at')->nullable();

            $table->integer('category_id');
            $table->integer('target_customer_sex');
            $table->integer('target_customer_age');

            $table->integer('payment_order');
            $table->integer('num_comment');
            $table->integer('num_view');
            $table->string('num_pop');

            $table->integer('money');
            $table->integer('point');

            $table->datetime('closed_at');
            $table->timestamps();
            $table->softDeletes();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('orders');
    }

}

update: 31 Oct 2018, Still usable on laravel 5.7 https://laravel.com/docs/5.7/migrations#modifying-columns

To make some change to existing db, you can modify column type by using change() in migration.

This is what you could do

Schema::table('orders', function ($table) {
    $table->string('category_id')->change();
});

please note you need to add doctrine/dbal dependency to composer.json for more information you can find it here http://laravel.com/docs/5.1/migrations#modifying-columns

The standard solution didn't work for me, when changing the type from TEXT to LONGTEXT.

I had to it like this:

public function up()
{
    DB::statement('ALTER TABLE mytable MODIFY mycolumn  LONGTEXT;');
}

public function down()
{
    DB::statement('ALTER TABLE mytable MODIFY mycolumn TEXT;');
}

This could be a Doctrine issue. More information here.

Another way to do it is to use the string() method, and set the value to the text type max length:

    Schema::table('mytable', function ($table) {
        // Will set the type to LONGTEXT.
        $table->string('mycolumn', 4294967295)->change();
    });

2018 Solution, still other answers are valid but you dont need to use any dependency:

First you have to create a new migration:

php artisan make:migration change_appointment_time_column_type

Then in that migration file up(), try:

    Schema::table('appointments', function ($table) {
        $table->string('time')->change();
    });

If you donot change the size default will be varchar(191) but If you want to change size of the field:

    Schema::table('appointments', function ($table) {
        $table->string('time', 40)->change();
    });

Then migrate the file by:

php artisan migrate

more info from doc.