warning: variable passed to each ..

PHP error is as follows:

warning: variable passed to each is not an array in
people/admin/update.inc line 75

original:

while(list(,$xtra)=each($xtramail)) {
if (!$xtra) {
continue;
}
$result_id=OPT_run_query($sql_id);
list($xtra_id)=OPT_fetch_row($result_id);
$sql="insert into mail_xtra set id='$xtra_id',
entry_type='people', entry_id='$id', email='$xtra'";
OPT_run_query($sql);
}

with fix:

if (is_array($xtramail)
{
while(list(,$xtra)=each($xtramail)) {
if (!$xtra) {
continue;
}
$result_id=OPT_run_query($sql_id);
list($xtra_id)=OPT_fetch_row($result_id);
$sql="insert into mail_xtra set id='$xtra_id',
entry_type='people', entry_id='$id', email='$xtra'";
OPT_run_query($sql);
}
}