include vs. require
If you are creating a PHP project and want the execution to go on, even if the included files may be missing, use the include statement since it will just give a warning and continue the file's execution.
If you are working on a complex PHP application like framework or CMS, and you want that the essential files must be present during the code execution. Always use the require statement since it will stop the execution and produce a fatal error in case of accidental missing of some vital files.
Must Read PHP Projects With Source Code
Example: Basic include
Let's assume we have a file called "dream.php" with a quote by Martin Luther King Jr.
<?php
$dream = 'dream that my four little children will one day live in a nation where they will not be judged by the color of their skin, but by the content of their character.';
// ~ Martin Luther King Jr.
?>
You can also try this code with Online PHP Compiler
Let's assume that some error occurred while including the above file.
Using include:
<html>
<body>
<h1>Welcome to Coding Ninjas!</h1>
<?php include 'dream.php';
echo "I have a $dream.";
?>
</body>
</html>
You can also try this code with Online PHP Compiler
Output:
Using require:
<html>
<body>
<h1>Welcome to Coding Ninjas!</h1>
<?php require 'dream.php';
echo "I have a $dream.";
?>
</body>
</html>
You can also try this code with Online PHP Compiler
Output:
Example: Including within functions
The dream.php is in the scope of fun(), so $dream is NOT available outside this scope. $anotherDream is available because we declared it as global.
<?php
function fun(){
global $anotherDream;
$anotherDream = “big dragon inside a small washing machine.” ;
include 'dream.php';
echo "I have a $dream \n";
}
fun();
echo "A $anotherDream";
?>
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Output:
Example: include through HTTP
This example assumes that www.example.com can parse .php files and not .txt files. 'Works' here means that the variable $dream is available within the included file.
<?php
// Won't work since file.txt isn't handled by www.example.com
include 'http://www.example.com/file.txt?dream=1&anotherdream=2';
// Won't work since it looks for a file named 'file.php?dream=1&anotherdream=2' in the local filesystem.
include 'file.php?dream=1&anotherdream=2';
// Works
include 'http://www.example.com/file.php?dream=1&anotherdream=2';
?>
You can also try this code with Online PHP Compiler
Output:
Example: Comparing return value of include
Below is an example that compares the return value of the include statement.
<?php
// won't work since it is evaluated as include(('dream.php') == TRUE), i.e., include('1')
if (include('dream.php') == TRUE) {
echo 'works';
}
// works
if ((include 'dream.php') == TRUE) {
echo 'works';
}
?>
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Output:
Example: include and the return statement
Here, we will see whether we can return a value in PHP include files.
return.php
<?php
$dream1 = 'PHP is love';
return $var;
?>
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noreturn.php
<?php
$dream2 = 'PHP is love with no returns';
?>
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test.php
<?php
$var = include 'return.php';
echo $var; // prints 'PHP is love'
$var1 = include 'noreturn.php';
echo $var1; // prints 1
?>
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Output:
Example: Using output buffering to have a PHP include file into a string
Use this method to include files within scripts automatically. Since this is a language construct and not a function, please don't call it using variable functions.
<?php
$string = get_include_contents('dream.php');
function get_include_contents($fileName) {
if (is_file($fileName)) {
ob_start();
include $fileName;
return ob_get_clean();
}
return false;
}
?>
You can also try this code with Online PHP Compiler
Frequently Asked Questions
1. What is PHP?
PHP is a scripting language used for backend web development. It is an open-source, decrypted server-side scripting language and supports object-oriented programming.
2. What are the advantages of using PHP?
There are many benefits of using PHP over other scripting languages. PHP is a server-side language suited for creating dynamic webpages. It is highly adaptable and provides compatibility and effortless integration. It supplies efficiency in performance and is cost-efficient.
3. Does reading PHP include files, slow down PHP script load?
PHP Include Files is similar to import in Java and python in that we use it for class and function definitions. Include should be extremely fast, but using it will delay script execution than if it was not there.
Key Takeaways
This article teaches about PHP Include Files and how we use them. We saw why PHP Include Files could be beneficial for a developer to learn. Click here to read about PHP Interview Questions.
Click here to see other related blogs on PHP.
Also, check out our web development course and blogs on Backend Web Technologies.
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