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/.
If filename begins with ../, it is looked only in
include_path relative to the current working directory.
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 16-5. 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
?>
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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 16-6. 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
?>
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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.
| Warning |
Windows versions of PHP
prior to PHP 4.3.0 do not support accessing remote files via this function, even if
allow_url_fopen is enabled.
|
Example 16-7. 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;
$bar = 2;
include 'file.txt'; // Works.
include 'file.php'; // Works.
?>
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See also
Remote files,
fopen() and
file() for related
information.
Because include() and require()
are special language constructs, you must enclose them within a statement
block if it's inside a conditional block.
Example 16-8. include() and conditional blocks
<?php
// This is WRONG and will not work as desired.
if ($condition)
include $file;
else
include $other;
// This is CORRECT.
if ($condition) {
include $file;
} else {
include $other;
}
?>
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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 16-9. 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';
}
?>
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Note:
In PHP 3, the return may not appear inside a block unless it's
a function block, in which case the return() applies
to that function and not the whole file.
Example 16-10. 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 $bar; // prints 1
?>
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$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 functions
defined after return().
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.
Note: Because this is a
language construct and not a function, it cannot be called using
variable functions
See also require(), require_once(),
include_once(), readfile(),
virtual(), and
include_path.