$s1 = 200;
$s2 = 300;
$pv = [
    'title' => [
        'text' => '总计：'.($s1 + $s2),
        'left' => 'center',
    ],
    'tooltip' => [
        'trigger' => 'item',
        'formatter' => '{b} : {c} ({d}%)',
    ],
    'legend' => [
        'orient' => 'vertical',
        'left' => 'left',
        'data' => ['PC端', '移动端'],
    ],
    'series' => [
        'type' => 'pie',
        'radius' => '55%',
        'center' => ['50%', '60%'],
        'data' => [
            [
                'value' => $s1,
                'name' => 'PC端',
            ],
            [
                'value' => $s2,
                'name' => '移动端',
            ],
        ],
        'emphasis' => [
            'itemStyle' => [
                'shadowBlur' => 10,
                'shadowOffsetX' => 0,
                'shadowColor' => 'rgba(0, 0, 0, 0.5)',
            ]
        ]
    ],
];

<div id="pv" style="height:300px;"></div>
<script>
    var myChart = echarts.init(document.getElementById('pv'));
    var option = {json_encode($pv)};
    myChart.setOption(option);
</script>