Dealing with deprecated or removed security-related functionality

Any changes to functionality that affect security are extremely important to note. Ignoring these changes can very easily lead not only to breaks in your code but can also open your websites to potential attackers. In this section, we cover a variety of security-related changes in functionality present in PHP 8. Let's start the discussion by examining filters.

Examining PHP 8 stream-filter changes

PHP input/output (I/O) operations depend upon a subsystem known as streams. One of the interesting aspects of this architecture is the ability to append a stream filter to any given stream. The filters you can append can be either custom-defined stream filters, registered using stream_filter_register(), or predefined filters included with your PHP installation.

An important change of which you need to be aware is that in PHP 8, all mcrypt.* and mdecrypt.* filters have been removed, as well as the string.strip_tags...