Experimentally I found that calling extract() also shows the number of keys if the key is set and is not numeric ! Maybe there was a better definition than mine . Please have a look to this scripts :
<?PHP
$var["i"] = "a";
$var["j"] = "b";
$var["k"] = 1;
echo extract($var); // returns 3
?>
<?PHP
$var2["i"] = "a";
$var2[2] = "b";
$var2[] = 1;
echo extract($var2); // returns 1
?>
(Arash Moslehi)