What are the functions htmlentities() and html_entity_decode() used for in PHP, and how can they be applied to address the issue of masked data conversion?

When dealing with masked data conversion, the issue arises when special characters in the data are not properly encoded or decoded, leading to potential security vulnerabilities or incorrect display of the data. To address this, we can use the htmlentities() function to convert special characters to HTML entities when storing the data, and then use html_entity_decode() function to decode the HTML entities back to their original characters when displaying the data.

// Storing data with htmlentities()
$maskedData = "<script>alert('Hello!')</script>";
$encodedData = htmlentities($maskedData);

// Displaying data with html_entity_decode()
$decodedData = html_entity_decode($encodedData);
echo $decodedData;