[jQuery] jQuery, ajax, json, php

[jQuery] jQuery, ajax, json, php


If I send a json format to php, how to get the value from php? for
example
front page
<script>
var jsonStr = '{"name": "David", "age", "23"}';
$.ajax({
    url: 'json.php',
    type: 'POST',
    cache: false,
    data: {json: jsonStr},
    success: function(data) {
        alert(data);
    }
});
</script>
php page
<?php
$json = $_POST['json'];
// it's get {"name":"David","age": "23"}, but how to gete name?
?>