+=item ut_foreign_key COLUMN FOREIGN_TABLE FOREIGN_COLUMN
+
+Check/untaint a foreign column key. Call a regular ut_ method (like ut_number)
+on the column first.
+
+=cut
+
+sub ut_foreign_key {
+ my( $self, $field, $table, $foreign ) = @_;
+ qsearchs($table, { $foreign => $self->getfield($field) })
+ or return "Can't find $field ". $self->getfield($field).
+ " in $table.$foreign";
+ '';
+}
+
+=item ut_foreign_keyn COLUMN FOREIGN_TABLE FOREIGN_COLUMN
+
+Like ut_foreign_key, except the null value is also allowed.
+
+=cut
+
+sub ut_foreign_keyn {
+ my( $self, $field, $table, $foreign ) = @_;
+ $self->getfield($field)
+ ? $self->ut_foreign_key($field, $table, $foreign)
+ : '';
+}
+