Including Files with include()
Monday, April 14th, 2008
The include() statement enables you to incorporate files into your PHP documents. PHP code in these files can be executed as if it were part of the main document. This can be useful for including library code in multiple pages.
Having created a killer function, your only option until now would have been to paste it into every document that needs to use it. Of course, if you discover a bug or want to add a feature, you would have to find every page that uses the function to make the change. The include() statement can save you from this chore. You can add the function to a single document and, at runtime, read it into any page that needs it. The include() statement requires a single argument: a relative path to the file to be included. 1.php creates a simple PHP script that uses include() to incorporate and output the contents of a file.
Using include()
1: <html>
2: <head>
3: <title>1.php Using include()</title>
4: </head>
5: <body>
6: <?php
7: include("2.php");
8: ?>
9: </body>
10: </html>
Put the above contents in a file named 1.php.
1: I have been included!!
put the above in a file named 2.php
The include() statement in 1.php incorporates the document 2.php
Place both files in your Web server document root. When you access 1.php through your Web browser, the output on the screen is
I have been included!!
This might seem strange to you, given that we’ve included plain text within a block of PHP code. In fact, the contents of an included file are displayed as text by default.
If you want to execute PHP code in an included file, you must enclose it in PHP start and end tags. In below examples , we amend the previous example so that code is executed in the included file.
Using the include() Statement to Execute PHP in Another File
1: <html>
2: <head>
3: <title>Using include to execute PHP in another file</title>
4: </head>
5: <body>
6: <?php
7: include("4.php");
8: ?>
9: </body>
10: </html>
Put the above contents in a file named 3.php
An Include File Containing PHP Code
1: <?php 2: print "I have been included!!<BR>"; 3: print "But now I can add up... 4 + 4 = ".(4 + 4); 4: ?>
Put the above code in a file named 4.php. Place both these files in your Web server document root. When you access 3.php through your Web browser, the output on the screen is
I have been included!! But now I can add up... 4 + 4 = 8
Returning a Value from an Included Document
Included files in PHP can return a value in the same way that functions do. As in a function, using the return statement ends the execution of code within the included file. Additionally, no further HTML is included. In below examples we include a file and assign its return value to a variable.
Using include() to Execute PHP and Assign the Return Value
1: <html>
2: <head>
3: <title>Using include() to execute PHP and
4: assign the return value</title>
5: </head>
6: <body>
7: <?php
8: $addResult = include("listing10.6.php");
9: print "The include file returned $addResult";
10: ?>
11: </body>
12: </html>
Put the above contents in a file named 5.php
An Include File That Returns a Value
1: <?php 2: $retval = (4 + 4); 3: return $retval; 4: ?> 5: This HTML will never be displayed because it comes after a return statement!
Put the above code in a file named 6.php. Place both of these files in your Web server document root. When you access listing10.5.php through your Web browser, the output is
The include file returned 8
Using include() Within Control Structures
You can use an include() statement in a conditional statement, and the referenced file is read only if the condition is met. For example, the include() statement in the following fragment will never be called:
$test = false;
if ($test) {
include("a_file.txt"); // won't be included
}
If you use an include() statement within a loop, it’s replaced with the contents of the referenced file each time the include() statement is called. This content is executed for every call. Below example illustrates this concept by using an include() statement in a for loop. The include() statement references a different file for each iteration.
Using include() Within a Loop
1: <html>
2: <head>
3: <title> Using include() within a loop</title>
4: </head>
5: <body>
6: <?php
7: for ( $x = 1; $x<=3; $x++ ) {
8: $incfile = "incfile$x".".txt";
9: print "Attempting include $incfile<br>";
10: include( "$incfile" );
11: print "<p>";
12: }
13: ?>
14: </body>
15: </html>
When above code is run, it includes the content of three different files: “incfile1.txt”, “incfile2.txt”, and “incfile3.txt”. Assuming that each of these files simply contains a confirmation of its own name.