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This article mainly introduces "how to configure the automatic loading of the PHP management dependency tool Composer". In the daily operation, I believe that many people have doubts about how to configure the PHP management dependency tool Composer automatic loading problem. The editor consulted all kinds of materials and sorted out a simple and easy-to-use operation method. I hope it will be helpful to answer the doubt of "how to configure the PHP management dependency tool Composer automatic loading". Next, please follow the editor to study!

For example, suppose our project wants to use monolog as a logging tool, we need to tell composer in composer.json that we need it:

{"require": {"monolog/monolog": "1.*"}}

Then execute:

Php composer.phar install

OK, now that the installation is finished, how to use it? Composer automatically generates an autoload file, you just need to reference it

Require'/ path/to/vendor/autoload.php'

Then it is very convenient to use the third-party class library, isn't it great! For the monolog we need, we can use it like this:

Use Monolog\ Logger;use Monolog\ Handler\ StreamHandler;// create a log channel$log = new Logger ('name'); $log- > pushHandler (new StreamHandler (' / path/to/log/log_name.log', Logger::WARNING)); / / add records to the log$log- > addWarning ('Foo'); $log- > addError (' Bar')

What did Composer do in the process? It generates an autoloader, and then according to each package's own autoload configuration, which helps us to load automatically. If you don't know much about this part of autoload, you can read my previous article

Next let's see how Composer does it.

For the automatic loading of third-party packages, Composer provides four ways to support the automatic loading of PSR-0 and PSR-4 (which I have also described in an article), generating class-map, and including files directly.

PSR-4 is recommended by composer because it is easier to use and leads to a more concise directory structure. This is how it is configured in composer.json:

{"autoload": {"psr-4": {"Foo\\": "src/",}

Key and value define namespace and the mapping to the corresponding path. According to PSR-4 rules, when you try to load the class "Foo\\ Bar\\ Baz" automatically, you will look for the file "src/Bar/Baz.php" and load it if it exists. Note that "Foo\"

Does not appear in the file path, which is different from PSR-0, if PSR-0 has this configuration, it will look for

"src/Foo/Bar/Baz.php"

This file.

Also note that in the configuration of PSR-4 and PSR-0, the namespace delimiter at the end of "Foo\" must be added and escaped to prevent accidents such as "Foo" matching to "FooBar".

After the composer is installed or updated, the configuration of the psr-4 is converted into the Map form of namespace to key,dir path to value and written into the generated vendor/composer/autoload_psr4.php file.

{"autoload": {"psr-0": {"Foo\\": "src/",}

Eventually this configuration is also written in the form of Map to the generated

Vendor/composer/autoload_namespaces.php

In the file.

Class-map is done by configuring the specified directory or file, and then when Composer installs or updates, it scans the class in the files ending in .php or .inc in the specified directory, generates a mapping of class to the specified file path, and adds it to the newly generated vendor/composer/autoload_classmap.php file.

{"autoload": {"classmap": ["src/", "lib/", "Something.php"]}}

For example, if there is a BaseController class under src/, this configuration will be generated in the autoload_classmap.php file:

'BaseController' = > $baseDir. '/ src/BaseController.php'

The Files way is to manually specify the files for direct loading. For example, we have a series of global helper functions, which can be put into a helper file and loaded directly.

{"autoload": {"files": ["src/MyLibrary/functions.php"]}}

It generates an array containing the files specified in these configurations, and then writes to the newly generated

Vendor/composer/autoload_files.php

File for autoloader to load directly.

Let's take a look at the code of composer autoload.

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