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PHP Include and Require

The include() and require() statements are extremely useful in PHP since they allow code to be reused across many scripts.

Include()

An include() file contains PHP statements and must be surrounded with the usual start and end script tags i.e. <?php and ?>.

An include() file may be saved with a .php file extension or a .inc file extension.

Note: If you save an include file with a .inc file extension and someone types the name of the file into the address box of their browser then they can view the contents of the file - this doesn't happen with a file saved with a .php file extension. This matters if you store passwords etc. in your include file.

It's useful to place functions, for example, within a separate file then use the include() statement within your scripts for them to be available.

The include() statement can be treated like any other PHP statement allowing conditional inclusions.

Example of include()

<?php
    if ($country == "US")
    {
        include ("settings_us.php");
    }
    else
    {
        include ("settings_uk.php");
    }
?>

Note: If a function is declared in a script that is already in an included file then it will produce an error.

Site maintenance is made much easier with included files. The header, footer and navigation can be saved in separate files then included in each web page. When a change is required it only needs one change to the included file.

Require()

This does exactly the same as include() except in the way that it handles failure.

Both include() and require() produce a warning but include() will continue processing - require() stops processing with a fatal error.

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