convert php array to json treeview
===

i have a json like this:(this is for treeview jquery plugin which load treeview by ajax)

    [
    {
        "text": "1. Pre Lunch (120 min)",
        "expanded": true,
        "classes": "important",
        "children":
        [
            {
                "text": "1.1 The State of the Powerdome (30 min)"
            },
             {
                "text": "1.2 The Future of jQuery (30 min)"
            },
             {
                "text": "1.2 jQuery UI - A step to richnessy (60 min)"
            }
        ]
    },
    {
        "text": "2. Lunch  (60 min)"
    },
    {
        "text": "3. After Lunch  (120+ min)",
        "children":
        [
            {
                "text": "3.1 jQuery Calendar Success Story (20 min)"
            },
             {
                "text": "3.2 jQuery and Ruby Web Frameworks (20 min)"
            },
             {
                "text": "3.3 Hey, I Can Do That! (20 min)"
            },
             {
                "text": "3.4 Taconite and Form (20 min)"
            },
             {
                "text": "3.5 Server-side JavaScript with jQuery and AOLserver (20 min)"
            },
             {
                "text": "3.6 The Onion: How to add features without adding features (20 min)",
                "id": "36",
                "hasChildren": true
            },
             {
                "text": "3.7 Visualizations with JavaScript and Canvas (20 min)"
            },
             {
                "text": "3.8 ActiveDOM (20 min)"
            },
             {
                "text": "3.8 Growing jQuery (20 min)"
            }
        ]
    }
]

I want write a php array Which return a json like this. please help me
I try several way to do it . bat i cannot do it.