$("#txtboxToFilter").keydown(function(event) {
 
  if ((event.keyCode == 8           // backspace
        || event.keyCode == 46    // delete
        || (event.keyCode >= 48 && event.keyCode <= 57)   // numbers on keyboard
        || (event.keyCode >= 96 && event.keyCode <= 105))// number on keypad
        ) {
           // Do Something
    }
});

<?php
$num=3;
$arr = array("1","2","3","4","5","6","7","8");
$count_arr=count($arr);
 
$arrName= array();
 
$idx=0;
 
while($idx<$num) 
{
	$id_rand = rand(0,$count_arr-1);
	if (!in_array($arr[$id_rand],$arrName))
	{
		$arrName[$idx]=$arr[$id_rand];
		$idx++;
	}
} 
 
print_r($arrName);
?>