You are looking at the HTML representation of the TXT format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the TXT format, set format=txt.
See the complete documentation, or API help for more information.
Array
(
    [query] => Array
        (
            [namespaces] => Array
                (
                    [-2] => Array
                        (
                            [id] => -2
                            [case] => first-letter
                            [*] => Media
                            [canonical] => Media
                        )

                    [-1] => Array
                        (
                            [id] => -1
                            [case] => first-letter
                            [*] => Special
                            [canonical] => Special
                        )

                    [0] => Array
                        (
                            [id] => 0
                            [case] => first-letter
                            [*] => 
                            [subpages] => 
                            [content] => 
                        )

                    [1] => Array
                        (
                            [id] => 1
                            [case] => first-letter
                            [*] => Talk
                            [subpages] => 
                            [canonical] => Talk
                        )

                    [2] => Array
                        (
                            [id] => 2
                            [case] => first-letter
                            [*] => User
                            [subpages] => 
                            [canonical] => User
                        )

                    [3] => Array
                        (
                            [id] => 3
                            [case] => first-letter
                            [*] => User talk
                            [subpages] => 
                            [canonical] => User talk
                        )

                    [4] => Array
                        (
                            [id] => 4
                            [case] => first-letter
                            [*] => RBEMWiki
                            [canonical] => Project
                        )

                    [5] => Array
                        (
                            [id] => 5
                            [case] => first-letter
                            [*] => RBEMWiki talk
                            [subpages] => 
                            [canonical] => Project talk
                        )

                    [6] => Array
                        (
                            [id] => 6
                            [case] => first-letter
                            [*] => File
                            [canonical] => File
                        )

                    [7] => Array
                        (
                            [id] => 7
                            [case] => first-letter
                            [*] => File talk
                            [subpages] => 
                            [canonical] => File talk
                        )

                    [8] => Array
                        (
                            [id] => 8
                            [case] => first-letter
                            [*] => MediaWiki
                            [subpages] => 
                            [canonical] => MediaWiki
                        )

                    [9] => Array
                        (
                            [id] => 9
                            [case] => first-letter
                            [*] => MediaWiki talk
                            [subpages] => 
                            [canonical] => MediaWiki talk
                        )

                    [10] => Array
                        (
                            [id] => 10
                            [case] => first-letter
                            [*] => Template
                            [canonical] => Template
                        )

                    [11] => Array
                        (
                            [id] => 11
                            [case] => first-letter
                            [*] => Template talk
                            [subpages] => 
                            [canonical] => Template talk
                        )

                    [12] => Array
                        (
                            [id] => 12
                            [case] => first-letter
                            [*] => Help
                            [canonical] => Help
                        )

                    [13] => Array
                        (
                            [id] => 13
                            [case] => first-letter
                            [*] => Help talk
                            [subpages] => 
                            [canonical] => Help talk
                        )

                    [14] => Array
                        (
                            [id] => 14
                            [case] => first-letter
                            [*] => Category
                            [canonical] => Category
                        )

                    [15] => Array
                        (
                            [id] => 15
                            [case] => first-letter
                            [*] => Category talk
                            [subpages] => 
                            [canonical] => Category talk
                        )

                    [100] => Array
                        (
                            [id] => 100
                            [case] => first-letter
                            [*] => Table
                            [canonical] => Table
                        )

                    [101] => Array
                        (
                            [id] => 101
                            [case] => first-letter
                            [*] => Table talk
                            [canonical] => Table talk
                        )

                    [274] => Array
                        (
                            [id] => 274
                            [case] => first-letter
                            [*] => Widget
                            [canonical] => Widget
                        )

                    [275] => Array
                        (
                            [id] => 275
                            [case] => first-letter
                            [*] => Widget talk
                            [subpages] => 
                            [canonical] => Widget talk
                        )

                    [500] => Array
                        (
                            [id] => 500
                            [case] => first-letter
                            [*] => Esperanto
                            [canonical] => Esperanto
                        )

                    [501] => Array
                        (
                            [id] => 501
                            [case] => first-letter
                            [*] => Esperanto paroli
                            [canonical] => Esperanto paroli
                        )

                    [502] => Array
                        (
                            [id] => 502
                            [case] => first-letter
                            [*] => Team
                            [subpages] => 
                            [canonical] => Team
                            [content] => 
                        )

                    [503] => Array
                        (
                            [id] => 503
                            [case] => first-letter
                            [*] => Team talk
                            [subpages] => 
                            [canonical] => Team talk
                        )

                    [828] => Array
                        (
                            [id] => 828
                            [case] => first-letter
                            [*] => Module
                            [subpages] => 
                            [canonical] => Module
                        )

                    [829] => Array
                        (
                            [id] => 829
                            [case] => first-letter
                            [*] => Module talk
                            [subpages] => 
                            [canonical] => Module talk
                        )

                    [1198] => Array
                        (
                            [id] => 1198
                            [case] => first-letter
                            [*] => Translations
                            [subpages] => 
                            [canonical] => Translations
                        )

                    [1199] => Array
                        (
                            [id] => 1199
                            [case] => first-letter
                            [*] => Translations talk
                            [subpages] => 
                            [canonical] => Translations talk
                        )

                )

        )

)