在jQuery .post中检索$ _POST

I have a select with some values.

When an option is selected I need to use .post in jQuery to send the selected value to a PHP function to obtain the $_POST variable on PHP.

Then I can use the variable to evaluate a condition on PHP.

I use CakePHP 2 to create a URL.

To assing the post URL to the numberOption variable.

                $( "#selectFilter" ).change(function() {
  var numberOption = "<?php echo $this->Html->url(array('action' => 'returnNumberOption/' ));?>" + 
  "/" + $( "#selectFilter option:selected" ).val();

  $.post(numberOption, function(data){
    console.log("Here is the number value of the select "+data);
    var phpVariable = "<?php echo $_POST?>"//THIS DONT WORK!
  });
}); 

Using this code I get an unexpected identifier error.

Question

How can I get the $_POST variable within the jQuery $.post call?

    var url = "<?php echo $this->Html->url(array('action' => 'returnNumberOption/' ));?>"; 
    var value = $( "#selectFilter option:selected" ).val();

     $.post(url,{data: value})
        .done(function(data){
        console.log("Here is the number value of the select "+data);
        var phpVariable = "<?php echo $_POST?>"//THIS DONT WORK!
    });

<?php
public function returnNumberOption() {
    if ($this->request->is('post')) {
        $data = $this->request->data;
    }
}