PHP: Detailed explanation of how to use require statement

require and include are almost identical, except for the way failure is handled. require generates an E_COMPILE_ERROR level error when an error occurs. In other words, it will cause the script to abort and include will only generate a warning ( E_WARNING ), and the script will continue to run.

Syntax

void require(string filename);

Description:

The parameter filename is the specified full path file name.

When using the require() statement to load a file, it will be executed as part of the PHP file. For example, if a mr.html web page file is loaded through the require() statement, then any PHP commands in the file will be processed. However, if the PHP script is simply placed in the HTML web page, It will not be processed.

As can be seen from the above analysis, PHP can use any extension to name include files, such as .inc files, html files or other non-standard extension files, etc., but PHP is usually used to parse files with extensions defined as .php. It is recommended that PHP website programmers use standard file extensions.

require() and include() Exactly the same in every way except how to deal with failure. include() produces a warning and require() results in a fatal error. In other words, if you want to stop processing a page when a file is missing, don't hesitate to use require() . This is not the case with include() and the script will continue to run. Also make sure the appropriate include_path is set.

<?php

require &#39;prepend.php&#39;;

require $somefile;

require (&#39;somefile.txt&#39;);
?>

Note: Prior to PHP 4.0.2 the following rule applied: require() will always try to read the target file, even if the line it is on will not be executed at all. Conditional statements do not affect require(). However, if the line where require() is located is not executed, the code in the target file will not be executed. Similarly, the loop structure does not affect the behavior of require(). Although the code contained in the target file is still the body of the loop, require() itself will only run once.

Note: Since this is a language structure rather than a function, it cannot be called by a "variable function".

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