ExtJs 4代理编写器和PHP $ _POST

Question

I have this store:

Ext.define('strMtoOrganismos', {
extend: 'Ext.data.Store',
model:  'mdlMtoOrganismos',
autoLoad: false,
pageSize: 20,
proxy: {
    type: 'ajax',
    api: {
        read: 'some php url',
        update: 'some php url'
    },
    reader: {
        type: 'json',
        root: 'data',
        totalProperty: 'total',
        successProperty: 'success'
    },
    writer: {
        type: 'json',
        root: 'data',
        encode: true,
        writeAllFields: false,
    }
}
});

In my controller I have a button that sync the store:

onPulsarGuardar:function(){
    Ext.getStore('strMtoOrganismos').sync();
}

And in my php file,printing $_POST[data] I receive for example: {"codigo_erp_cliente":"243","id":2}

How can I convert this string to an array like:

[codigo_erp_cliente]=>243

[id]=>2

Or an alternative configuration to the store writer?