I have a input text field. I need to pass the values entered inside the element through onClick of javascript.

<form>

<fieldset>     

  <label>Common Site ID: </label><span><?php echo $commonsiteid ?></span><br>

  <label>Acres: </label><input id=acre_value name=acre_value type=text value=<?php echo $acre; ?>>

 </fieldset>

</form>

<input type=submit value=submit onclick=saveValue('<?php echo $_REQUEST['acre_value'] ?>')>

I am passing the value through submit onClick, Which is going empty. How do i pass value in this onclick function.