Passing a javascript array to a php page using post method

Have a look into JSON encoding.

In PHP you can decode it using json_decode, not quite sure how you'll encode it in Javascript but it is possible

http://en.wikipedia.org/wiki/JSON

using jQuery

 $.post("test.php", { 'choices[]': ["Jon", "Susan"] });

Edit

if you are creating ajax object and using it then I'll suggest to convert your data in query string send it through ajax object.

like :

var  userdetails = [1,2,3,4];
var queryString = "";
for(i=0; i<userdetails.length; i++){
queryString = queryString + 'userdetails[]='+userdetails[i]+'&';
}

connect.send(queryString) 

example posting with json

var array = [1,2,3,4,5,6];
$.ajax({
  url: "mydomain.com/url",
  type: "POST",
  dataType: "json",
  data: {arrayName: array},
  complete: function() {
    //called when complete
  },
  success: function() {
    //called when successful
  },
  error: function() {
    //called when there is an error
  },
});

Then the json could be parsed server side.

arrays can also be sent using application/x-www-form-urlencoded - this is the default format for submitting.