Possible PostTypes: 
Array
(
    [0] =&gt; Array
        (
            [ID] =&gt; post
            [value] =&gt; post
        )

    [1] =&gt; Array
        (
            [ID] =&gt; page
            [value] =&gt; page
        )

    [2] =&gt; Array
        (
            [ID] =&gt; attachment
            [value] =&gt; attachment
        )

    [3] =&gt; Array
        (
            [ID] =&gt; options
            [value] =&gt; options
        )

    [4] =&gt; Array
        (
            [ID] =&gt; portfolio
            [value] =&gt; portfolio
        )

)
