In FireFox, if you put `xbegin()` and `xend()` outside of body,
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<?php HObfus::xbegin(); ?>
<body>

<h3>Test Doctype</h3>

</body>
<?php HObfus::xend(); ?>
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then you will receive the following warning:
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An unbalanced tree was written using document.write() causing data from the network to be reparsed. More information: https://developer.mozilla.org/en-US/docs/Glossary/speculative_parsing
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To remove the warning, you need to put `xbegin()` and `xend()` inside <body>.
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<body>
<?php HObfus::xbegin(); ?>

<h3>Test Doctype</h3>

<?php HObfus::xend(); ?>
</body>
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Also, adding them inside `head` works too.
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<head>
<?php HObfus::xbegin(); ?>


<?php HObfus::xend(); ?>
</head>
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