differentFrom()

Use differentFrom() when two fields must not contain the same value.

ValidationRegistry::register(
    Profile::class,
    static fn (RuleSet $rules): array => [
        $rules->string('newUsername')->differentFrom('currentUsername'),
    ]
);

The failure code is different_from.

The comparison uses the current field’s value and the named property on the same object. It passes when the values are not strictly equal.

$profile = new Profile();
$profile->currentUsername = 'alice';
$profile->newUsername = 'alice';

$error = Rule::for($profile)
    ->string('newUsername')
    ->differentFrom('currentUsername')
    ->validate();

Use object-bound or handler validation so the related field can be read from the same object.

The closure form receives the object and returns the value that must differ from the current field:

$rule = Rule::for($profile)
    ->string('newUsername')
    ->differentFrom(static fn (Profile $profile): string => $profile->currentUsername);