Require and include are terms used in PHP. Both are being used to carry out different functions in PHP and are written in this form include (), require (). However, it is essential to note that both are not functions but are referred to as constructs. The main difference between them is that include (), is used to include a specified file, firstly it gives a warning if it could not find the file to include, and then continue the script execution. While for require (), it also includes specified folder, but if the file has been added already, it will not cover it again, it will give a fatal error. If it is unable to find the file, it will stop the script execution.
If the data being included is critical to the rest of the script running correctly, then you need to use require. When going through the code building process, you are quickly going to notice fatal errors if any thrown by requiring and you can, therefore, make needed corrections before finally completing the script. However, you should perhaps use include to prepare an alternative strategy if things didn't go as smoothly as planned.