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
                            [*] => 
                            [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
                            [*] => MediaWiki
                            [subpages] => 
                            [canonical] => Project
                        )

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

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

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

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

                    [104] => Array
                        (
                            [id] => 104
                            [case] => first-letter
                            [*] => Type
                            [canonical] => Type
                        )

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

                    [106] => Array
                        (
                            [id] => 106
                            [case] => first-letter
                            [*] => Form
                            [canonical] => Form
                        )

                    [107] => Array
                        (
                            [id] => 107
                            [case] => first-letter
                            [*] => Form talk
                            [subpages] => 
                            [canonical] => Form talk
                        )

                    [108] => Array
                        (
                            [id] => 108
                            [case] => first-letter
                            [*] => Book
                            [canonical] => Book
                        )

                    [109] => Array
                        (
                            [id] => 109
                            [case] => first-letter
                            [*] => Book talk
                            [canonical] => Book talk
                        )

                    [170] => Array
                        (
                            [id] => 170
                            [case] => first-letter
                            [*] => Filter
                            [canonical] => Filter
                        )

                    [171] => Array
                        (
                            [id] => 171
                            [case] => first-letter
                            [*] => Filter talk
                            [subpages] => 
                            [canonical] => Filter talk
                        )

                    [420] => Array
                        (
                            [id] => 420
                            [case] => first-letter
                            [*] => Layer
                            [canonical] => Layer
                        )

                    [421] => Array
                        (
                            [id] => 421
                            [case] => first-letter
                            [*] => Layer talk
                            [canonical] => Layer talk
                        )

                    [446] => Array
                        (
                            [id] => 446
                            [case] => first-letter
                            [*] => Education Program
                            [canonical] => Education Program
                        )

                    [447] => Array
                        (
                            [id] => 447
                            [case] => first-letter
                            [*] => Education Program talk
                            [canonical] => Education Program talk
                        )

                    [490] => Array
                        (
                            [id] => 490
                            [case] => first-letter
                            [*] => Profile
                            [canonical] => Profile
                        )

                    [491] => Array
                        (
                            [id] => 491
                            [case] => first-letter
                            [*] => Profile talk
                            [canonical] => Profile 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
                        )

                )

        )

)