json_encode and highcharts

I'm trying to make graphs in PHP and MySQL using jQuery, specifically with Highcharts library, I have managed to make the chart with data from MySQL database, but these data show some data if they are in the databases but not others, for example, a query that yields 10 results 5 are good, but the other five did not, I have done some research on the web and I understand it is due to a problem when I pass the result of my query in MySQL by json_encode, I hope some of you can tell me because I have this error or if I'm misusing the JSON, thank you very much. Code: index.php

    <html>
<head> 
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> 
    <title>Incidencias</title>
    <script type="text/javascript" src="../js/jquery-1.7.1.min.js" ></script>
    <script type="text/javascript" src="../js/highcharts.js" ></script>
    <script type="text/javascript" src="../js/themes/grid.js"></script>
    <script type="text/javascript" src="../js/export.js"></script>
    <script type="text/javascript">
        var chart;
            $(document).ready(function() {
                var options = {
                    chart: {
                        renderTo: 'pieClientes',
                        defaultSeriesType: 'pie',
                        marginRight: 10,
                        marginBottom: 25
                    },
                    title: {
                        text: 'top 10. Clientes con m\u00e1s incidencias',
                        x: -10  
                    },
                    subtitle: {
                        text: '',
                        x: -20
                    },
                    tooltip: {
                        formatter: function() {
                            return '<b>'+ this.point.name +'</b>: <b>'+ this.y +' incidencias</b>';
                        }
                    },
                    legend: {
                        layout: 'vertical',
                        align: 'right',
                        verticalAlign: 'top',
                        x: -10,
                        y: 100,
                        borderWidth: 0
                    },

                series: [{
                    type: 'pie',
                    name: 'Browser share',
                    data: []
                }]
            }

            $.getJSON("datosCliente.php", function(json) {
                options.series[0].data = json;
                chart = new Highcharts.Chart(options);
            });
            });
    </script>
</head>
<body>
    <div style="font-size: 12p; font-family: Calibri, Candara, Segoe, Segoe UI, Optima, Arial, sans-serif; align="left" >
        <h1>Dashboard incidencias SCI</h1>
    <div>
    <div id="pieClientes" style="width: 770px; height: 450x; margin: 0"></div>              
</body>
</html>

datosCliente.php

<?php
    include"../clases/conexion.php";
    $result = mysql_query("SELECT 
                    clientes.cliente,
                    COUNT(incidencias.idIncidencia) AS nIncidencias
                    FROM incidencias
                    INNER JOIN clientes ON incidencias.idCliente = clientes.idCliente
                    GROUP BY incidencias.idCliente
                    ORDER BY nIncidencias DESC
                    LIMIT 0,10");
    $rows = array();
        while($r = mysql_fetch_array($result)) 
            {
                $row[0] = $r[0];
                $row[1] = $r[1];
                array_push($rows,$row);
            }

    //print json_encode($rows, JSON_PRETTY_PRINT);
    echo json_encode($rows, JSON_NUMERIC_CHECK | JSON_PRETTY_PRINT); 
    mysql_close($con);
?>

The error is for example when I want to show 10 row of the database in the graph, it show me the results of this form:

      1st. row->  show me "slice" 
      2nd. row-> the registerok,
      3th. row->  show me "slice"
      4. row-> the registerok,
      5. row-> the registerok,
      6.row-> show me "slice"
     7.row->the registerok,
     8.row-> show me "slice"
     9.row->the registerok,
    10.row-> show me "slice"

The problem is that in the graph (pie) displays correct data but not others, it is as if some records or tubiese skipped a limit of 5 registrros, not I do not know where I'm wrong. :(

thanks for helping :)

First of all I would try to give the array elements a value, instead of using the index. Give your array key a name. As well remove all the uppercase letters from your encode. I am on an ipad and unable to code, but let me know if you have questions.