html / php:用php获取列表值

I'm trying to get the value of the li the client clicked on and 'transform' that into a php variable.

<ul class="dropdown-menu" role="menu">
    <li id="banAppeal"><a href="#">Ban Appeal</a></li>
    <li id="banAppeales"><a href="#">Spanish Ban Appeal</a></li>
</ul>

If they click on "Ban Appeal", a form appears:

$(document).ready(function(){
  $("#banAppeal").click(function(){
    $("table#unban").show();
    $("table#default").hide();
  }); });

How can I get the value of whatever they click and put that in a PHP Variable? I know .val() does not work.

To send a variable or a value to PHP, you either need to utilize
POST
GET
AJAX

here are some example codes in how you can do so.
http://iviewsource.com/codingtutorials/learning-how-to-use-jquery-ajax-with-php-video-tutorial/

Javascript is client side, and PHP server side. So you can't use JavaScript / JQuery with PHP Take a look to AJAX, it can help you

If I got your need, "the value of whatever they click" it could be achieved like this.

$(document).on("click", ".yourClassControl", function(e){
        e.preventDefault();
        var dt={ 
                   ObjId:$(this).attr("id"), //This is the variable you will //send to PHP as you asked... NOTE: you said "the value of whatever they click" //so, for each DOM element you will have different way to retrieve the id 
                   otherData:$(this).val()
                };
      var request =$.ajax({//http://api.jquery.com/jQuery.ajax/
                            url: "ADMIN/ADMIN.php",
                            type: "POST",
                            data: dt,
                            dataType: "json"  //I use JSON in this example   
                    }); //End of $.ajax({...

           request.fail(function(jqXHR, textStatus) {
                      alert("Request failed: " + textStatus);
                    });//End of fail(function....


           request.done(function(dataset){//This will receive the information  //from your PHP page and use this information to control the beheavior of your //DOM elements 
               for (var index in dataset){ 
                   responseFromPHP=dataset[index].responPHP;
                }//End of for

             $('.wrapper').html(responseFromPHP);

         }); //End of request.done(....






  }); //Endo of  $(document).on("click", ...

PHP side:

I have used AJAX whit JSON response from PHP. ADMIN.php

$ObjEvn=$_POST["ObjId"];//Here is your question.... ObjId comes from javascript  // and $ObjEvn is your php variable

if($ObjEvn==="banAppeal"){
   //Do something for banAppeal element
}
elseif($ObjEvn==="banAppeales"){
   //Do something for banAppeales element
}

//Now return what you want to javascript

$arrToJSON = array(
        "responPHP"=>"your value or string or code"
        );  
        return json_encode(array($arrToJSON));