require()
The require() statement includes and evaluates the specific file.
require() includes and evaluates a specific file. Detailed information on how this inclusion works is described in the documentation for include().
require() and include() are identical in every way except how they handle failure. They both produce a Warning, but require() results in a Fatal Error. In other words, don't hesitate to use require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. Be sure to have an appropriate include_path setting as well.
Example#1 Basic require() examples
<?php
require 'prepend.php';
require $somefile;
require ('somefile.txt');
?>
See the include() documentation for more examples.
Note: Prior to PHP 4.0.2, the following applies: require() will always attempt to read the target file, even if the line it's on never executes. The conditional statement won't affect require(). However, if the line on which the require() occurs is not executed, neither will any of the code in the target file be executed. Similarly, looping structures do not affect the behaviour of require(). Although the code contained in the target file is still subject to the loop, the require() itself happens only once.
Note: 由於這是一個語言結構而非函式，因此它無法被變數函式呼叫。
PHP 4.3.0 之前的 Windows PHP版本，即使啟動allow_url_fopen選項，也不支援由此函式存取遠端檔案。
See also include(), require_once(), include_once(), get_included_files(), eval(), file(), readfile(), virtual() and include_path.