What CSS properties can be used to hide the content of a PHP variable in a web page?

To hide the content of a PHP variable in a web page, you can use CSS properties like "display: none;" or "visibility: hidden;". By applying these CSS properties to the HTML element that displays the PHP variable, you can effectively hide the content from being visible on the webpage while still keeping it in the page source code.

<?php
$hiddenContent = "This is the content to be hidden";
?>

<!DOCTYPE html>
<html>
<head>
<style>
.hidden {
    display: none;
}
</style>
</head>
<body>
<p>This content will be visible</p>
<p class="hidden"><?php echo $hiddenContent; ?></p>
</body>
</html>