PHP include/require

Description

With include statement we can import reusable code and reuse it.

Syntax

Including other PHP files is done by include keyword.

or

Example

For example, consider the following file, foo.php:

<?php/*from  w  ww . java 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  www. j a v  a 2s . c o  m
       print "Starting foo";
       print "In bar";
       print "Finishing foo";
?>

PHP includes a file if the include line is actually executed.

<?php/*from   ww w . j  a  v  a 2  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_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.