The require function is used to include a file into PHP code. However there is one difference between the two functions. When you include a file with the include function and PHP cannot find it you will see a warning message while when you include a file with the require function and PHP cannot find it you will see a fatal error message.
During require execution if fatal error occurs in case file is missing or name is incorrect, then the script will cease to run further and will halt there.
<?php require("somefile.php"); ?>