php - 配列の要素を抽出する

Question

json_decode を介して返された配列があり、以下の image_url のみを抽出したいと考えています。以下のimage_urlを取得するには、これからどのphpコマンドを実行しますか?

[0] => 
    stdClass Object ( 
        [id] => 36210508 
        [name] => Untitled 
        [description] => 
        [times_viewed] => 2 
        [rating] => 0 
        [created_at] => 2013-05-31T15:08:36-04:00 
        [category] => 0 
        [privacy] => 
        [width] => 275 
        [height] => 183 
        [votes_count] => 0 
        [favorites_count] => 0 
        [comments_count] => 0 
        [nsfw] => 
        [license_type] => 0 
        [image_url] => http://pcdn.500px.net/36210508/5de3b4bb9cdee9f429e2a329a1d0619dd5b28ce1/4.jpg 
        [images] => 
            Array ( 
                [0] => 
                stdClass Object ( 
                    [size] => 4 
                    [url] => http://pcdn.500px.net/36210508/5de3b4bb9cdee9f429e2a329a1d0619dd5b28ce1/4.jpg 
                )
            )
        [store_download] => 
        [store_print] => 
        [user] => 
        stdClass Object ( 
            [id] => 3677956 
            [username] => jsniff12 
            [firstname] => Jacob 
            [lastname] => Sniff 
            [city] => 
            [country] => 
            [fullname] => Jacob Sniff 
            [userpic_url] => /graphics/userpic.png 
            [upgrade_status] => 0 
            [followers_count] => 0 
            [affection] => 0 
        )
    )
)