Work with multilevel arrays

Hi, I am learning PHP and came to this tiered array after using print_r on $this->root

 Array ( 
    [0] => 9 
    [obj] => 3562 
    [gen] => 0 
    [1] => Array ( 
        [0] => 5 
        [1] => Array ( 
            [/AcroForm] => Array ( 
                [0] => 8 
                [1] => 3563 
                [2] => 0 
                ) 
            [/Metadata] => Array ( 
                [0] => 8 
                [1] => 3559 
                [2] => 0 
                ) 
            [/PageLabels] => Array ( 
                [0] => 8 
                [1] => 3389 
                [2] => 0 
                ) 
            [/Pages] => Array ( 
                [0] => 8 
                [1] => 3392 
                [2] => 0 
                ) 
            [/Type] => Array ( 
                [0] => 2 
                [1] => /Catalog 
                ) 
            ) 
        ) 
    ) Array ( 
        [0] => 9 
        [obj] => 8 
        [gen] => 0 
        [1] => Array ( 
            [0] => 5 
            [1] => Array ( 
                [/Type] => Array ( 
                    [0] => 2 
                    [1] => /Catalog 
                    ) 
                [/Pages] => Array ( 
                    [0] => 8 
                    [1] => 1 
                    [2] => 0 
                    ) 
                [/OpenAction] => Array ( 
                    [0] => 6 
                    [1] => Array ( 
                        [0] => Array ( 
                            [0] => 8 
                            [1] => 3 
                            [2] => 0 
                            ) 
                        [1] => Array ( 
                            [0] => 2 
                            [1] => /FitH 
                            ) 
                        [2] => Array ( 
                            [0] => 0 
                            ) 
                        ) 
                    ) 
                [/PageLayout] => Array ( 
                    [0] => 2 
                    [1] => /OneColumn 
                    ) 
                ) 
            ) 
        ) 

I have a question about the behavior of multilevel arrays, I want to use this function

$pages = $this->pdf_resolve_object($this->c, $this->root[1][1]['/Pages']);

and $this->root[1][1]['/Pages'], which, I believe, are used to check the array for these keys, and if it exists, use pdf_resolve_object as a variable

so my question is 2 times, one - does it $this->root[1][1]['/Pages']check the array and pass through the keys? if not, what is his behavior? and 2, when it checks the array, it goes through only 4 top keys or all sub-keys?

If someone can help or connect me with some training materials that will be much appreciated, thanks!