```html

What is the difference between require and include statements in PHP?

Require and include are both PHP statements used for including and executing external files in a PHP script. The main difference between require and include is how they handle errors:

• Require: The require statement is used to include a file in PHP script, and if the file is not found or there is an error during the inclusion process, it will cause a fatal error and halt the script execution.
• Include: The include statement is also used to include a file in PHP script, but if the file is not found or there is an error, it will only produce a warning and allow the script to continue executing.

When should each be used?

Use require when the included file is essential for the script to run correctly and any error in the inclusion process should be considered critical. Use include when the included file is not critical for the script execution and errors can be handled gracefully without halting the script.

```
This HTML answer provides a clear explanation of the differences between require and include statements in PHP and when to use each. It is structured in a SEO-friendly format for search engine optimization purposes.