Banilla87

Thanks but the field is always saved and no error is returned!
I show you that code just for example. My original one is:

// ADD FIELD
function add_additional_user_meta( $profileuser ) {

   // here my input fields
   <input type="text" size="20" name="user_pec" id="user_pec" value="<?php echo esc_attr( $profileuser->user_pec ); ?>" />

}
add_action('show_user_profile', 'add_additional_user_meta');
add_action('edit_user_profile', 'add_additional_user_meta');

// SAVE FIELD
function save_additional_user_meta( $user_id ) {
   // here I save fields
   update_user_meta( $user_id, 'user_pec', sanitize_text_field( $_POST['user_pec'] ) );
}
add_action( 'personal_options_update', 'save_additional_user_meta' );
add_action( 'edit_user_profile_update', 'save_additional_user_meta' );

// CHECK FIELD
function check_fields($errors, $update, $user){
   // here make some validation
    if ( ! isset( $_POST['user_pec'] ) ) {
        $errors->add( 'empty_user_pec', __( '<strong>ERROR</strong>: Insert e-mail PEC.' ), array( 'form-field' => 'user_pec' ) );
    } elseif ( !is_email( $_POST['user_pec'] ) ) {
        $errors->add( 'invalid_user_pec', __( '<strong>ERROR</strong>: not valid e-mail PEC' ), array( 'form-field' => 'user_pec' ) );
    } elseif ( ( $owner_id = email_exists($_POST['user_pec']) ) && ( !$update || ( $owner_id != $user->ID ) ) ) {
        $errors->add( 'user_pec_exists', __('<strong>ERROR</strong>: Already exist'), array( 'form-field' => 'user_pec' ) );
    }
   }
}
add_filter('user_profile_update_errors', 'check_fields', 10, 3);

Last function seems not work!
If I put a number inside the field, error appears but the field is saved however!

Any idea?