some basic javascript syntax

1) array operation
var a = new Array();

101) read a php variable
<table>
    <tr>
        <button name="submit_type" type="submit" value="insert">insert</button>
    </tr>
    <tr>
        <button name="submit_type" type="submit" value="search">search</button>
    </tr>
</table>

<script language="JavaScript">
    var php_submit_type_val = <?php echo json_encode($_POST[submit_type]) ?>;
</script>