PHP include/require
In this chapter you will learn:
- Why do we need to include another PHP file
- Syntax to include other files
- Example - include file
- How and when to use require keyword
- include_once() and require_once()
Description
With include statement we can import reusable code and reuse it.
Syntax
Including other PHP files is done by include keyword.
include 'fileName.php';
or
require 'fileName.php';Example
For example, consider the following file, foo.php:
<?php//from j a va 2 s .com
print "Starting foo";
include 'bar.php';
print "Finishing foo";
?>
And also the file bar.php:
<?php
print "In bar";
?>
PHP would load the file bar.php, read in its contents, then put it into foo.php in place of the include 'bar.php' line.
Therefore, foo.php would look like this:
<?php//from j a v a 2s.c om
print "Starting foo";
print "In bar";
print "Finishing foo";
?>
PHP includes a file if the include line is actually executed.
<?php// j a v a2 s . c o m
if (3 > 9) {
include 'bar.php';//never include bar.php
}
?>
require
Including a non-existing file will generate a warning message.
PHP has the require keyword, which will halt script execution if called on a non-existing file.
We usually put common functions, object definitions, and layout code into a file and then use include to reuse them.
For example, to reuse header on every page, we can start each of your pages with this:
include 'header.php';include_once() and require_once()
include_once() and require_once() operate in the same way as include and require, respectively.
They will only include a file once. Include_once and require_once share the same list of already-included files.
When including or requiring a file, PHP first checks the directory in which the script is running, then it looks in its include path. The include path is defined in your php.ini file using the include_path directive.
The get_included_files() and get_required_files() functions tell the names of the included files.
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What you will learn in the next chapter: