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.

all other answers are Correct But Before you run

php artisan migrate

make sure you run this code first

composer require doctrine/dbal

to avoid this error

> RuntimeException : Changing columns for table "items" requires Doctrine DBAL; install "doctrine/dbal".

First composer requires doctrine/dbal, then:

$table->longText('column_name')->change();

Not really an answer, but just a note about ->change():

> Only the following column types can be "changed": bigInteger, binary, boolean, date, dateTime, dateTimeTz, decimal, integer, json, longText, mediumText, smallInteger, string, text, time, unsignedBigInteger, unsignedInteger and unsignedSmallInteger.

https://laravel.com/docs/5.8/migrations#modifying-columns

If your column isn't one of these you will need to either drop the column or use the alter statement as mentioned in other answers.

For me the solution was just replace unsigned with index

This is the full code:

    Schema::create('champions_overview',function (Blueprint $table){
        $table->engine = 'InnoDB';
        $table->increments('id');
        $table->integer('cid')->index();
        $table->longText('name');
    });


    Schema::create('champions_stats',function (Blueprint $table){
        $table->engine = 'InnoDB';
        $table->increments('id');
        $table->integer('championd_id')->index();
        $table->foreign('championd_id', 'ch_id')->references('cid')->on('champions_overview');
    });