We create a lot of migrations if we are developing a large project so mistakes are possible. How will you change a table if the migration is already created? Let's see.

Laravel 5 supports changing columns

Schema::table('users', function($table)
{

    $table->string('name', 50)->nullable()->change();
});

For Laravel 4, you should install DBAL package using composer.

composer require doctrine/dbal

 Then you need to write raw sql commands. 

$app =app();
$laravelVer= explode('.',$app::VERSION); 
    switch ($laravelVer[0]) {       
    case('5') :                           
        Schema::table('pro_categories_langs', function(Blueprint $t) {              
        $t->string('name', 100)->nullable()->default(null)->change();          
        });                         
        break;                               
    default :                           
        DB::statement('ALTER TABLE `pro_categories_langs` MODIFY `name`VARCHAR(100) NULL;');
    }