If you are developing web applications with PHP, you may want to reuse some code from one file in another file. This can help you avoid repeating yourself, maintain consistency, and organize your code better. In this article, you will learn how to include a PHP file in another file using two different methods: the include and require statements.
The include statement allows you to insert the contents of another PHP file into the current file. This means that any variables, functions, classes, or other code elements defined in the included file will be available in the current file. The syntax of the include statement is simple: just write include 'filename.php'; where you want the included file to appear. You can use either absolute or relative paths to specify the filename. For example, include 'header.php'; will include the file named header.php in the same directory as the current file, while include '/var/www/html/footer.php'; will include the file named footer.php in the specified absolute path.
The PHP language provides two functions for including a file in a program: "include" and "require" functions. It is highly recommended not to include a file based on URL query strings, as this can lead to vulnerabilities in our application. Attackers may exploit this vulnerability to launch various attacks, such as Local File Inclusion (LFI) and Remote File Inclusion (RFI), allowing them to execute malicious programs and gain full access to our server.
To include a PHP file in another PHP file, you can use the include or require statements. These statements allow you to insert the content of one PHP file into another PHP file before the server executes it. Using include The include statement will attempt to include the specified file, but if the file is not found, it will continue executing the script without causing an error. PHP <?php // Include the 'functions.php' file include 'functions.php'; // Use a function from the included file echo greet('Bard'); ?>
"Include" and "Require" can be used, use require when the file is required by the application. Use include when the file is not required and application should continue when file is not found.
You can include a php file in another file using an 'include' statement. Example; <?php include 'my_include_file.php'; ?>
PHP makes it possible to include the content of one PHP file into another. This basically means you can copy the whole content of a PHP file and use it into other one. This happens with the use of two function statements and they are include and require. To use, just add a line include 'filename.php' to the top of the current working PHP file. Or alternative for the above statement is require 'filename.php' which I would recommend strongly as it is secure. In order to understand the above statements better, lets take an example of a PHP script in which I have a very long array to use and that array is a global one. So what we can do is save that whole array variable in a separate PHP file and then include it wherever it is required.
The require statement is similar to the include statement, except that it will stop the execution of the script if the included file is not found or has an error. This means that the require statement is more strict and ensures that the included file is essential for the script to run. The syntax of the require statement is the same as the include statement: just write require 'filename.php'; where you want the included file to appear. You can also use absolute or relative paths to specify the filename. For example, require 'config.php'; will require the file named config.php in the same directory as the current file, while require '/var/www/html/functions.php'; will require the file named functions.php in the specified absolute path.
The require statement does the same thing as include statement, with an exception that when the file doesn’t not exist in the location specified in the required statement, the script stops execution and throws a fatal error.
Unlike "include," which warns and allows script continuation if a specified file isn't found, "require" causes a fatal error, halting the script on file load failure. This strictness ensures crucial files load correctly, preventing incomplete execution. For apps dependent on security files (e.g., authorization, various configuration files) or crucial components, "require" mandates their presence. This shields against scripts operating without essentials, averting unexpected behavior or vulnerabilities. Also, it notably reduces runtime errors due to missing files.
The require statement in PHP serves a similar purpose to include, with the key difference being its strictness; if the file specified cannot be found or has an error, the script will halt execution. This makes require suitable for files that are critical to the application, such as configuration files or shared functions. The syntax is straightforward: require 'filename.php'; is placed where the contents of 'filename.php' need to be included in the script. Both relative and absolute paths can be used to locate the file, ensuring that your script only proceeds with all necessary components correctly loaded. For instance, require 'config.php'; mandates the presence of 'config.php' in the same directory for the script to continue execution.
The PHP programming language offers two functions, namely "include" and "require", which can be used to incorporate a file into a program. Avoid incorporating a file through URL query strings, as this can expose our application to potential vulnerabilities. Malicious individuals can potentially take advantage of this vulnerability to carry out many types of attacks, including Local File Inclusion (LFI) and Remote File Inclusion (RFI). These attacks enable them to execute harmful programs and obtain complete control over our server. The "include" statement allows the script to continue executing even if the file is not found or the inclusion fails. On the other hand, the "require" statement causes the script to stop immediately.
include: Use include 'filename.php'; Generates a warning if the file is not found but allows the script to continue. require: Use require 'filename.php'; Generates a fatal error if the file is not found, halting script execution. include_once: Use include_once 'filename.php'; Includes the file only once to prevent redeclaration issues. require_once: Use require_once 'filename.php'; Includes the file only once, generating a fatal error if the file is not found.
If you want to include a PHP file only once in your script, you can use the include_once or require_once statements. These statements will check if the file has already been included or required before, and if so, they will not include or require it again. This can prevent errors or conflicts caused by multiple declarations of the same variables, functions, classes, or other code elements. The syntax of the include_once and require_once statements is the same as the include and require statements: just write include_once 'filename.php'; or require_once 'filename.php'; where you want the included file to appear. You can also use absolute or relative paths to specify the filename. For example, include_once 'header.php'; or require_once 'header.php'; will include or require the file named header.php only once in the script, regardless of how many times it is called.
The include_once and require_once statements in PHP are enhancements of the include and require statements that ensure a file is included only a single time within a script. This is particularly useful to avoid issues like redeclaration of functions, classes, or variable conflicts that might arise when the same file is included multiple times. The syntax for both is straightforward: include_once 'filename.php'; or require_once 'filename.php'; can be added where the inclusion is needed. These statements first check if the file has already been included and if not, proceed with the inclusion. This feature maintains code efficiency and integrity, whether using relative paths, like include_once 'config.php';, or absolute paths.
The include_once and require_once statements do the same thing, as include and require respectively except that if they will check whether the file was included/required earlier before they load again. If at all they were included/required earlier, they will not be loaded again.
require_once and include_once Are far better options than require and include in my experience as it caters for human error or when working with badly documented code or frameworks. As a general rule of thumb, I teach my juniors to rather use *_once functions when it doubt.
include: Use include 'filename.php'; Generates a warning if the file is not found but allows the script to continue. require: Use require 'filename.php'; Generates a fatal error if the file is not found, halting script execution. include_once: Use include_once 'filename.php'; Includes the file only once to prevent redeclaration issues. require_once: Use require_once 'filename.php'; Includes the file only once, generating a fatal error if the file is not found.
Including PHP files in your web applications can offer numerous benefits. Reusing common code elements, such as headers, footers, menus, or functions, across multiple pages or scripts can save time and effort while making your code more maintainable and consistent. Additionally, separating your code into smaller chunks rather than one large and complex file can improve readability and structure. Modularizing your code and creating libraries or frameworks of reusable code can also enhance functionality and quality while making it more scalable and extensible.
Including PHP files is highly beneficial for web development, as it facilitates code reuse and maintenance, ensuring that common elements like headers and footers remain consistent across different pages. This practice leads to a more organized and readable codebase, streamlining updates and debugging. Moreover, it enables modular programming, allowing developers to build scalable and extensible applications by creating libraries of reusable code that can easily be maintained and enhanced over time.
Apart from the obvious OOP advantages there are also performance advantages to breaking your code up into multiple files. For example let say you have a large file with thousands of lines of code that performs a very specific set of task, having this code interpreted every single page load would slow down the server side processing, and in configs where content is only rendered after the server side processing is complete this would result is slowed load times which would negatively impact the user experience. In the land of load times, milliseconds count.
Modularity: Break code into smaller, manageable files for easier organization. Separation of Concerns: Group related functions or settings in separate files. DRY Principle: Reduce redundancy by reusing common code across multiple scripts. Easier Updates: Updates without affecting the entire codebase. Collaboration: Facilitates collaboration and assignments. Facilitates Growth: Manage complexity as your project expands. Load Files as Needed: Include files based on specific conditions, optimizing resource usage. Autoloading: Implement autoloading for efficient class inclusion in larger projects. Encapsulate Functionality: Group specific functionality in files and include them where needed.
When you include PHP files in your web applications, you should follow some best practices to avoid errors or issues. Start by using descriptive and meaningful filenames for your included files, and stick to a consistent naming convention. This can help you identify and locate your files easily, and prevent confusion or duplication. Additionally, use relative paths instead of absolute paths to specify the filenames of your included files. This can make your code more portable and flexible, and help you avoid problems when you move or change your files or directories. Further, use the include_once or require_once statements when you include files that contain definitions of variables, functions, classes, or other code elements that should not be repeated. This can prevent errors or conflicts caused by multiple declarations of the same code elements. Lastly, use the require statement when you include files that are essential for your script to run, and use the include statement when you include files that are optional or supplementary. This can help you handle errors or exceptions gracefully, and make sure your script doesn't break if the included file is not found or has an error.
In 2023 you SHOULD NOT use manual includes in PHP. Use a PSR-compatible autoloader instead, such as the one supplied as part of Composer (it's actually a standard in the php development world)
Best practices for including PHP files aim to ensure efficient, error-free code. Always use meaningful and consistent filenames to avoid confusion and facilitate easy file management. Opt for relative paths when specifying the location of included files to increase code portability and avoid issues during migration or directory changes. For files containing classes, functions, or variable definitions, utilize include_once or require_once to guard against multiple inclusions that can lead to conflicts. Choose require for critical files necessary for application operation and include for those that are optional, allowing for more graceful error handling and maintaining script integrity even if an included file encounters issues.
Best practice: Use PSR-4 autoloading via Composer Worst practice: `eval(file_get_contents('http(no "s")://randomwebsite.com'))`
Always include PHP files with require_once() to prevent duplicate inclusions and ensure code consistency. Use absolute paths for file resolution and follow a consistent naming convention. Document your includes for better understanding.
Like any other programming language, such as C++, Java, or Python. The choices and their inclusion are arranged hierarchically, allowing prewritten code libraries or snippets to be quickly repurposed in new scripts. This encourages modularity and reusability without the need to reinvent the wheel.
If I'll see a code with "include/require" statement inside - the developer will be fired in 5 minutes. Use Autoloader and Namespaces. Do not write manual includes.
The most important factor is to be able to identify the correct type of statement to use. `require` will generate error if it cannot find the file, but some times you might want to optionally include the file, use `include` in that case. Also, use the magic constant `__DIR__` when including from the current directory or parent or sub directories, so that you won't have to write the whole absolute path yourself.
There are 2 statements for including the file which helps in reusing the code. 1. Require or require_once: if the file content is a must piece of code then this statement can be used to make sure without this the execution gets stopped. 2. Include or include_once: This can be used when the program execution is not going to affect the content of the PHP file is missing. The required_once or include_once will only load the content of the file once and thus avoids the chances for duplicate variable or function or class declaration errors. But in modern PHP programing we use composer with auto loading feature other than directly including the PHP file.
By properly using PHP include/require statements you can create modular and reusable code. It also can be useful to enhance team collaboration.
As other may already pointed out this is a not so-good way to include a PHP file in another. I think there is still usage for this in many case. Such as templating. Originally, PHP was mean to be a templating language. And `include` & `require` concept align very well with that purpose. Aside from templating. Use autoload would be a better way, straightforward and best practice to include a PHP file in another file in larger project. Not only benefit from security perspective, you will also likely gain extra performance for using autoloader as it will only include the class (file) that actually used.