Как мне получить доступ к свойствам объектов, в которые помещен объект javascript?

У меня есть php файл, который отправляет json-строку объектов в файл javascript. У меня возникают проблемы с доступом к свойствам объектов, которые содержатся в этом объекте javascript.

Мой php файл:

 for($i=0; $i<$hitcount; $i++){
        if($i == $hitcount-1){
            // IF HITCOUNT IS LESS THAN 25 RESULTS
            echo json_encode($articleArray);
            exit();
        }else if($i == 25){
            // THERE IS ONLY A MAX OF 25 RESULTS PER REQUEST
            echo json_encode($articleArray);
            exit();
        }else{
            $page = $xml -> request  -> page ; //always page 1

    $title = $xml ->resultList -> result[$i] -> title;
        if($title == false){
            $title = '';
        }

    $pmid = $xml ->resultList -> result[$i] -> pmid;
        if($pmid == false){
            $pmid = '';
        }

    $authorString = $xml ->resultList -> result[$i] -> authorString;
        if($authorString == false){
            $authorString ='';
        }
    $journalTitle  = $xml ->resultList -> result[$i] -> journalTitle ;
        if($journalTitle ==false){
            $journalTitle = '';
        }
    $pubYear = $xml ->resultList -> result[$i] -> pubYear;
        if($pubYear == false){
            $pubYear = '';
        }
    $journalVolume = $xml ->resultList -> result[$i] -> journalVolume;
        if($journalVolume == false){
            $journalVolume = '';
        }
    $issue = $xml ->resultList -> result[v] -> issue;
        if($issue == false){
            $issue = '';
        }
    $pageInfo = $xml ->resultList -> result[$i] -> pageInfo;
        if($pageInfo == false){
            $pageInfo = '';
        }


        $articleArray[] = array(
            'hitCount' => $hitcount,
            'page' => $page,
            'pmid' => $pmid,
            'title' => $title,
            'authors' => $authorString,
            'journalTitle' => $journalTitle,
            'pubYear' => $pubYear,
            'journalVolume' => $journalVolume,
            'issue' => $issue,
            'pageInfo' => $pageInfo
            );
        }
    }

мой файл javascript:

 // Retrieve json string
var json_obj = JSON.parse(xmlhttp.responseText);

Я попробовал следующее для доступа к свойствам объектов, которые хранятся в объекте javascript:

 json_obj[0].title // to access the title of the first object

Это просто возвращает:

 [object Object]

xmlhttp.responseText:

 [{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25745995"},"title":{"0":"Hypoxia upregulates Rab11-family interacting protein 4 through HIF-1\u03b1 to promote the metastasis of hepatocellular carcinoma."},"authors":{"0":"Hu F, Deng X, Yang X, Jin H, Gu D, Lv X, Wang C, Zhang Y, Huo X, Shen Q, Luo Q, Zhao F, Ge T, Zhao F, Chu W, Shu H, Yao M, Fan J, Qin W."},"journalTitle":{"0":"Oncogene"},"pubYear":{"0":"2015"},"journalVolume":"","issue":"","pageInfo":""},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25800835"},"title":{"0":"Kinetic activation of Rab8 guanine nucleotide exchange factor Rabin8 by Rab11."},"authors":{"0":"Feng S, Wu B, Per\u00e4nen J, Guo W."},"journalTitle":{"0":"Methods Mol Biol"},"pubYear":{"0":"2015"},"journalVolume":{"0":"1298"},"issue":"","pageInfo":{"0":"99-106"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"26032412"},"title":{"0":"Structure-Function Analyses of the Interactions Between Rab11 and Rab14 Small GTPases with their Shared Effector Rab Coupling Protein (RCP)."},"authors":{"0":"Lall P, Lindsay A, Hanscom S, Kecman T, Taglauer ES, McVeigh UM, Franklin E, McCaffrey MW, Khan AR."},"journalTitle":{"0":"J Biol Chem"},"pubYear":{"0":"2015"},"journalVolume":"","issue":"","pageInfo":""},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25815277"},"title":{"0":"Rab11 in disease progression."},"authors":{"0":"Bhuin T, Roy JK."},"journalTitle":{"0":"Int J Mol Cell Med"},"pubYear":{"0":"2015"},"journalVolume":{"0":"4"},"issue":"","pageInfo":{"0":"1-8"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25800843"},"title":{"0":"In vitro and in vivo characterization of the Rab11-GAP activity of Drosophila Evi5."},"authors":{"0":"Laflamme C, Emery G."},"journalTitle":{"0":"Methods Mol Biol"},"pubYear":{"0":"2015"},"journalVolume":{"0":"1298"},"issue":"","pageInfo":{"0":"187-194"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"24917558"},"title":{"0":"Vasodilator-stimulated phosphoprotein promotes activation of hepatic stellate cells by regulating Rab11-dependent plasma membrane targeting of transforming growth factor beta receptors."},"authors":{"0":"Tu K, Li J, Verma VK, Liu C, Billadeau DD, Lamprecht G, Xiang X, Guo L, Dhanasekaran R, Roberts LR, Shah VH, Kang N."},"journalTitle":{"0":"Hepatology"},"pubYear":{"0":"2015"},"journalVolume":{"0":"61"},"issue":"","pageInfo":{"0":"361-374"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25480917"},"title":{"0":"Vangl2 cooperates with Rab11 and Myosin V to regulate apical constriction during vertebrate gastrulation."},"authors":{"0":"Ossipova O, Chuykin I, Chu CW, Sokol SY."},"journalTitle":{"0":"Development"},"pubYear":{"0":"2015"},"journalVolume":{"0":"142"},"issue":"","pageInfo":{"0":"99-107"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25831508"},"title":{"0":"TRAPPII regulates exocytic Golgi exit by mediating nucleotide exchange on the Ypt31 ortholog RabERAB11."},"authors":{"0":"Pinar M, Arst HN Jr, Pantazopoulou A, Tagua VG, de los R\u00edos V, Rodr\u00edguez-Salarichs J, D\u00edaz JF, Pe\u00f1alva MA."},"journalTitle":{"0":"Proc Natl Acad Sci U S A"},"pubYear":{"0":"2015"},"journalVolume":{"0":"112"},"issue":"","pageInfo":{"0":"4346-4351"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25305083"},"title":{"0":"Rab11 modulates \u03b1-synuclein-mediated defects in synaptic transmission and behaviour."},"authors":{"0":"Breda C, Nugent ML, Estranero JG, Kyriacou CP, Outeiro TF, Steinert JR, Giorgini F."},"journalTitle":{"0":"Hum Mol Genet"},"pubYear":{"0":"2015"},"journalVolume":{"0":"24"},"issue":"","pageInfo":{"0":"1077-1091"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25862161"},"title":{"0":"A novel role of Rab11 in trafficking GPI-anchored trans-sialidase to the plasma membrane of Trypanosoma cruzi."},"authors":{"0":"Niyogi S, Docampo R."},"journalTitle":{"0":"Small GTPases"},"pubYear":{"0":"2015"},"journalVolume":{"0":"6"},"issue":"","pageInfo":{"0":"8-10"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25673879"},"title":{"0":"The Arf and Rab11 effector FIP3 acts synergistically with ASAP1 to direct Rabin8 in ciliary receptor targeting."},"authors":{"0":"Wang J, Deretic D."},"journalTitle":{"0":"J Cell Sci"},"pubYear":{"0":"2015"},"journalVolume":{"0":"128"},"issue":"","pageInfo":{"0":"1375-1385"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25972173"},"title":{"0":"Synaptic Function of Rab11Fip5: Selective Requirement for Hippocampal Long-Term Depression."},"authors":{"0":"Bacaj T, Ahmad M, Jurado S, Malenka RC, S\u00fcdhof TC."},"journalTitle":{"0":"J Neurosci"},"pubYear":{"0":"2015"},"journalVolume":{"0":"35"},"issue":"","pageInfo":{"0":"7460-7474"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25632160"},"title":{"0":"Myosin Va mediates BDNF-induced postendocytic recycling of full-length TrkB and its translocation into dendritic spines."},"authors":{"0":"Sui WH, Huang SH, Wang J, Chen Q, Liu T, Chen ZY."},"journalTitle":{"0":"J Cell Sci"},"pubYear":{"0":"2015"},"journalVolume":{"0":"128"},"issue":"","pageInfo":{"0":"1108-1122"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25686250"},"title":{"0":"Early steps in primary cilium assembly require EHD1\/EHD3-dependent ciliary vesicle formation."},"authors":{"0":"Lu Q, Insinna C, Ott C, Stauffer J, Pintado PA, Rahajeng J, Baxa U, Walia V, Cuenca A, Hwang YS, Daar IO, Lopes S, Lippincott-Schwartz J, Jackson PK, Caplan S, Westlake CJ."},"journalTitle":{"0":"Nat Cell Biol"},"pubYear":{"0":"2015"},"journalVolume":{"0":"17"},"issue":"","pageInfo":{"0":"228-240"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25904794"},"title":{"0":"Protein Interacting with C-Kinase 1 Deficiency Impairs Glutathione Synthesis and Increases Oxidative Stress via Reduction of Surface Excitatory Amino Acid Carrier 1."},"authors":{"0":"Wang YN, Zhou L, Li YH, Wang Z, Li YC, Zhang YW, Wang Y, Liu G, Shen Y."},"journalTitle":{"0":"J Neurosci"},"pubYear":{"0":"2015"},"journalVolume":{"0":"35"},"issue":"","pageInfo":{"0":"6429-6443"}},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"26041286"},"title":{"0":"Intracellular Transport of Vaccinia Virus in HeLa Cells Requires WASH-VPEF\/FAM21-Retromer Complexes and Recycling molecules Rab11 and Rab22."},"authors":{"0":"Hsiao JC, Chu LW, Lo YT, Lee SP, Chen TJ, Huang CY, Ping YH, Chang W."},"journalTitle":{"0":"J Virol"},"pubYear":{"0":"2015"},"journalVolume":"","issue":"","pageInfo":""},{"hitCount":{"0":"3347"},"page":{"0":"1"},"pmid":{"0":"25704914"},"title":{"0":"Mechanisms regulating cell membrane localization of the chemokine receptor CXCR4 in human hepatocarcinoma cells."},"authors":{"0":"Cepeda EB, Dediulia T, Fernando J, Bertran E, Egea G, Navarro E, Fabregat I."},"journalTitle":{"0":"Biochim Biophys 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