$mas=array();
$mas['a1']=array('a1_aaa', 'a1_fff', 'a1_zzz');
$mas['a2']=array('a2_aaa', 'a2_fff', 'a2_zzz');
$mas['a3']=array('a3_aaa', 'a3_fff', 'a3_zzz');

$code="<script>\n";
$code.="var mas=new Array();\n";
foreach($mas as $key=>$value)
{
   $code.="mas['".$key. "']=new Array();\n";
   foreach($value as $key1=>$value1)
      $code.="mas['".$key. "'][".$key1. "]='".$value1. "';\n";
}
$code.="
function reselect(value)
{
   var input_a2;
   var input_a3;

   input_a2=document.getElementById('a2');
   input_a3=document.getElementById('a3');

   input_a2.value=mas['a2'][value];
   input_a3.value=mas['a3'][value];
}
";
$code.="</script>";

foreach($mas['a1'] as $key=>$value)
{
   $options.="<option value='".$key. "'>".$value. "</option>";
}

$code.="
<select id='a1' onChange='reselect(this.value)'>
   $options
</select>
<input id='a2' value=''>
<input id='a3' value=''>
<script>reselect(0)</script>
";

echo $code;