Answers for "foreign id on existing column laravel"

foreign id laravel migration

$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

foreignId in laravel

// for laravel 7 or above. 
$table->foreignId('user_id')->constrained();
/*-----------OR---------------*/
$table->foreignId('user_id')->constrained('users');