<body>
<div> <?= $_POST['msg'] ?> </div>
<form id="frm" method="post">
<input type="hidden" name='msg' value='{"field0": "Im a string", "field1": 84, "field3": "so am I"}' />
<input type="submit" value="test" />
</form>
</body>
<body>
<div> <?= $_POST['msg'] ?> </div>
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