Code Generation¶

Code generation is the automatic production of source code from a higher-level specification, model, schema, or set of rules. Rather than writing repetitive or boilerplate code by hand, a generator reads a description and emits the corresponding PHP source, which is then used directly or compiled into the application.

Code generation takes several forms:

Schema-driven generation: an ORM such as Doctrine generates entity classes, migration files, and repository stubs from a database schema or mapping configuration.
Attribute-driven generation: attributes on classes, properties, and methods, in versions 8.0+, are read by tools such as Symfony’s DI container or Doctrine to emit container configuration, proxy classes, or metadata caches as a build step.
Scaffolding: frameworks such as Laravel, with artisan make:*`, and Symfony, make:entity, make:controller, generate controllers, models, migrations, and test stubs from a single command.
Proxy generation: libraries such as ocramius/proxy-manager emit subclass proxies at runtime or ahead of time to implement lazy loading, access interception, or decoration without touching the original class.
AST rewriting: nikic/php-parser parses PHP source into an AST, applies transformations via a visitor, and regenerates source, used by Rector for automated refactoring and upgrade migrations.
Template-based generation: tools such as twig or custom scripts emit PHP classes, configuration files, or API clients from templates.

Generated code is typically committed to the repository, so that deployment does not require a build step, or kept out of version control and regenerated as part of CI. The choice depends on whether the generated output is considered an artefact or a first-class source file.

Code generation differs from metaprogramming in that it produces static files before runtime; metaprogramming operates on the live program at runtime.

<?php

    // Doctrine: generate entity proxy classes ahead of time (CLI build step)
    // php vendor/bin/doctrine orm:generate-proxies

    // Symfony: scaffold a new entity with make:entity
    // php bin/console make:entity User

    // nikic/php-parser: generate a getter method and write it back to the file
    use PhpParser\BuilderFactory;
    use PhpParser\PrettyPrinter\Standard;

    $factory = new BuilderFactory();
    $method  = $factory->method('getName')
        ->makePublic()
        ->setReturnType('string')
        ->addStmt(new \PhpParser\Node\Stmt\Return_(
            new \PhpParser\Node\Expr\PropertyFetch(
                new \PhpParser\Node\Expr\Variable('this'), 'name'
            )
        ))
        ->getNode();

    $printer = new Standard();
    echo $printer->prettyPrint([$method]);

?>

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Code Generation¶

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