What is the correct syntax for including files in PHP and why is using the "?=0" unnecessary?

When including files in PHP, the correct syntax is to use `include` or `require` followed by the file path in quotes. Using `?=` is unnecessary and can cause syntax errors. The `?=` is typically used for echoing variables, not for including files.

// Correct way to include a file in PHP
include 'myfile.php';