solved: why an 'Undefined index:' ?

[eluser]danmontgomery[/eluser]

Code:

$list = array(
array('name' => 'jan', 'where' => array('ks_datum >=' => '2010-01-01', 'ks_datum =<' => '2010-01-31')),
array('name' => 'feb', 'where' => array('ks_datum >=' => '2010-02-01', 'ks_datum =<' => '2010-02-28')),
array('name' => 'mrz', 'where' => array('ks_datum >=' => '2010-03-01', 'ks_datum =<' => '2010-03-31')),
array('name' => 'apr', 'where' => array('ks_datum >=' => '2010-04-01', 'ks_datum =<' => '2010-04-30'))
);