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
                            [*] => WikiResearcher
                            [subpages] => 
                            [canonical] => Project
                            [content] => 
                        )

                    [5] => Array
                        (
                            [id] => 5
                            [case] => first-letter
                            [*] => WikiResearcher 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
                            [canonical] => MediaWiki
                        )

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

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

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

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

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

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

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

                    [90] => Array
                        (
                            [id] => 90
                            [case] => first-letter
                            [*] => Thread
                            [subpages] => 
                            [canonical] => Thread
                        )

                    [91] => Array
                        (
                            [id] => 91
                            [case] => first-letter
                            [*] => Thread talk
                            [subpages] => 
                            [canonical] => Thread talk
                        )

                    [92] => Array
                        (
                            [id] => 92
                            [case] => first-letter
                            [*] => Summary
                            [subpages] => 
                            [canonical] => Summary
                        )

                    [93] => Array
                        (
                            [id] => 93
                            [case] => first-letter
                            [*] => Summary talk
                            [subpages] => 
                            [canonical] => Summary talk
                        )

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

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

                    [102] => Array
                        (
                            [id] => 102
                            [case] => first-letter
                            [*] => Practice
                            [subpages] => 
                            [canonical] => Practice
                        )

                    [103] => Array
                        (
                            [id] => 103
                            [case] => first-letter
                            [*] => Practice talk
                            [subpages] => 
                            [canonical] => Practice talk
                        )

                    [104] => Array
                        (
                            [id] => 104
                            [case] => first-letter
                            [*] => OERF
                            [subpages] => 
                            [canonical] => OERF
                            [content] => 
                        )

                    [105] => Array
                        (
                            [id] => 105
                            [case] => first-letter
                            [*] => OERF talk
                            [subpages] => 
                            [canonical] => OERF talk
                        )

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

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

                    [460] => Array
                        (
                            [id] => 460
                            [case] => case-sensitive
                            [*] => Campaign
                            [canonical] => Campaign
                            [defaultcontentmodel] => Campaign
                        )

                    [461] => Array
                        (
                            [id] => 461
                            [case] => case-sensitive
                            [*] => Campaign talk
                            [canonical] => Campaign talk
                        )

                    [710] => Array
                        (
                            [id] => 710
                            [case] => first-letter
                            [*] => TimedText
                            [canonical] => TimedText
                        )

                    [711] => Array
                        (
                            [id] => 711
                            [case] => first-letter
                            [*] => TimedText talk
                            [canonical] => TimedText 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
                        )

                )

        )

)