保存为.html和.php时画布上绘图的差异

screenshot of canvas.php When i drew on to canvas and saved it as .php file then it looks blurry than when saved as .html file. I dont understand why this is happening? canvas.html is very clear in comparison to canvas.php .

body, html {
width: 100%;
height: 100%;
margin: 0;
padding: 0;
overflow: hidden;
background-color: green;
}
canvas {
position:absolute;
background-color: black;
}
</style>
</head>
<body>

<canvas id="canvas" height="400" width="500"></canvas>
<script type="text/javascript">
 var canvas=document.getElementById('canvas'),
 ctx=canvas.getContext('2d');
 ctx.fillStyle="red";
 ctx.font="100px bold cursive";
 ctx.fillText("Hello",134,145);

</script>

</html>

Someone please clarify me the reason.

Thanks!

screenshot of canvas.html