include()

The include() statement includes and evaluates the specified file.

The documentation below also applies to require(). The two constructs are identical in every way except how they handle failure. include() produces a Warning while require() results in a Fatal Error. In other words, 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. Be warned that parse error in required file doesn't cause processing halting.

Files for including are first looked in include_path relative to the current working directory and then in include_path relative to the directory of current script. E.g. if your include_path is ., current working directory is /www/, you included include/a.php and there is include "b.php" in that file, b.php is first looked in /www/ and then in /www/include/.

When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward.

Example 15-3. Basic include() example vars.php <?php $color = 'green'; $fruit = 'apple'; ?> test.php <?php echo "A $color $fruit"; // A include 'vars.php'; echo "A $color $fruit"; // A green apple ?>

If the include occurs inside a function within the calling file, then all of the code contained in the called file will behave as though it had been defined inside that function. So, it will follow the variable scope of that function.

Example 15-4. Including within functions <?php function foo() {     global $color;     include 'vars.php';     echo "A $color $fruit"; } /* vars.php is in the scope of foo() so     * * $fruit is NOT available outside of this  * * scope.  $color is because we declared it * * as global.                               */ foo();                    // A green apple echo "A $color $fruit";   // A green ?>

When a file is included, parsing drops out of PHP mode and into HTML mode at the beginning of the target file, and resumes again at the end. For this reason, any code inside the target file which should be executed as PHP code must be enclosed within valid PHP start and end tags.

If "URL fopen wrappers" are enabled in PHP (which they are in the default configuration), you can specify the file to be included using a URL (via HTTP or other supported wrapper - see Appendix L for a list of protocols) instead of a local pathname. If the target server interprets the target file as PHP code, variables may be passed to the included file using a URL request string as used with HTTP GET. This is not strictly speaking the same thing as including the file and having it inherit the parent file's variable scope; the script is actually being run on the remote server and the result is then being included into the local script.

Example 15-5. include() through HTTP <?php /* This example assumes that www.example.com is configured to parse .php * files and not .txt files. Also, 'Works' here means that the variables * $foo and $bar are available within the included file. */ // Won't work; file.txt wasn't handled by www.example.com as PHP include 'http://www.example.com/file.txt?foo=1&bar=2'; // Won't work; looks for a file named 'file.php?foo=1&bar=2' on the // local filesystem. include 'file.php?foo=1&bar=2'; // Works. include 'http://www.example.com/file.php?foo=1&bar=2'; $foo = 1; $bar = 2; include 'file.txt';  // Works. include 'file.php';  // Works. ?>

See also Remote files, fopen() and file() for related information.

Because include() and require() are special language constructs, you must enclose them within a statement block if it's inside a conditional block.

Example 15-6. include() and conditional blocks <?php // This is WRONG and will not work as desired. if ($condition)     include $file; else     include $other; // This is CORRECT. if ($condition) {     include $file; } else {     include $other; } ?>

Handling Returns: It is possible to execute a return() statement inside an included file in order to terminate processing in that file and return to the script which called it. Also, it's possible to return values from included files. You can take the value of the include call as you would a normal function. This is not, however, possible when including remote files unless the output of the remote file has valid PHP start and end tags (as with any local file). You can declare the needed variables within those tags and they will be introduced at whichever point the file was included.

Because include() is a special language construct, parentheses are not needed around its argument. Take care when comparing return value.

Example 15-7. Comparing return value of include <?php // won't work, evaluated as include(('vars.php') == 'OK'), i.e. include('') if (include('vars.php') == 'OK') {     echo 'OK'; } // works if ((include 'vars.php') == 'OK') {     echo 'OK'; } ?>

Example 15-8. include() and the return() statement return.php <?php $var = 'PHP'; return $var; ?> noreturn.php <?php $var = 'PHP'; ?> testreturns.php <?php $foo = include 'return.php'; echo $foo; // prints 'PHP' $bar = include 'noreturn.php'; echo $bar; // prints 1 ?>

$bar is the value 1 because the include was successful. Notice the difference between the above examples. The first uses return() within the included file while the other does not. If the file can't be included, FALSE is returned and E_WARNING is issued.

If there are functions defined in the included file, they can be used in the main file independent if they are before return() or after. If the file is included twice, PHP 5 issues fatal error because functions were already declared, while PHP 4 doesn't complain about it. It is recommended to use include_once() instead of checking if the file was already included and conditionally return inside the included file.

A few other ways to "include" files into variables are with fopen(), file() or by using include() along with Output Control Functions.

See also require(), require_once(), include_once(), readfile(), virtual(), and include_path.