Composer & Autoloading

Autoloading

The function spl_autoload_register() allows to register a function that will be invoked when PHP needs to load a class/interface defined by the user.

In autoload.php:

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# custom function
function autoloader($class) {


    # __DIR__ -> path of calling file
    # $class -> className (hopefully same as file)
    # if class is in namespace $class -> Namespace\className (hopefully folders mirror Namespace)

    $class = str_replace("\\", DIRECTORY_SEPARATOR, $class);  # avoid linux path separator issues

    $fileName = sprintf("%s\\path\\%s.php", __DIR__, $class);  
    # or
    $filename = sprintf("%s\\%s.php", __DIR__, $class);  # if class is in namespace

    if (file_exists($fileName)) {
        include $fileName;
    }
}

spl_autoload_register('autoloader');  // register function

In file.php:

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require "autoload.php";

# other code

Note: will fuck up if namespaces exists.

Multiple Autoloading

It's possible to resister multiple autoloading functions by calling spl_autoload_register() multiple times.

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# prepend adds the function at the start of the queue
# throws selects if errors in loading throw exceptions
spl_autoload_register(callable $func, $throw=TRUE, $prepend=FALSE);

spl_autoload_functions()  # return a list of registered functions.

Composer

Open Source project for dependency management and autoloading of PHP libraries and classes.

Composer uses composer.json to define dependencies with third-party libraries. Libraries are downloaded through Packagist and GitHub.

In composer.json:

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{
    "require": {
        "php": ">=7.0",
        "monolog/monolog": "1.0.*"
    }
}

Installing Dependencies

In the same folder of composer.json execute composer install.

Composer will create:

• vendor: folder containing all requested libraries
• vendor\autoload.php: file for class autoloading
• composer.lock

In alternative composer require <lib> will add the library to the project and create a composer.json if missing.

Note: to ignore the php version use composer <command> --ignore-platform-reqs

Updating Dependencies

To update dependencies use composer update. To update only the autoloading section use composer dump-autoload.

Autoloading Project Classes

PSR-4 Spec

Composer can also autoload classes belonging to the current project. It's sufficient to add the autoload keyword in the JSON and specify the path and autoload mode.

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{
    "autoload": {
        "psr-4": {
            "RootNamespace": "src/",
            "Namespace\\": "src/Namespace/",
            },
        "file": [
            "path/to/file.php",
            ...
        ]
    }
}