Conventions

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The Coding Standards document describes the coding standards for the Symfony projects and the internal and third-party bundles. This document describes coding standards and conventions used in the core framework to make it more consistent and predictable. You are encouraged to follow them in your own code, but you don't need to.

Method Names

When an object has a "main" many relation with related "things" (objects, parameters, ...), the method names are normalized:

get()
set()
has()
all()
replace()
remove()
clear()
isEmpty()
add()
register()
count()
keys()

The usage of these methods is only allowed when it is clear that there is a main relation:

a CookieJar has many Cookie objects;
a Service Container has many services and many parameters (as services is the main relation, the naming convention is used for this relation);
a Console Input has many arguments and many options. There is no "main" relation, and so the naming convention does not apply.

For many relations where the convention does not apply, the following methods must be used instead (where XXX is the name of the related thing):

Main Relation	Other Relations
`get()`	`getXXX()`
`set()`	`setXXX()`
n/a	`replaceXXX()`
`has()`	`hasXXX()`
`all()`	`getXXXs()`
`replace()`	`setXXXs()`
`remove()`	`removeXXX()`
`clear()`	`clearXXX()`
`isEmpty()`	`isEmptyXXX()`
`add()`	`addXXX()`
`register()`	`registerXXX()`
`count()`	`countXXX()`
`keys()`	n/a

Note

While "setXXX" and "replaceXXX" are very similar, there is one notable difference: "setXXX" may replace, or add new elements to the relation. "replaceXXX", on the other hand, cannot add new elements. If an unrecognized key is passed to "replaceXXX" it must throw an exception.

Deprecations

From time to time, some classes and/or methods are deprecated in the framework; that happens when a feature implementation cannot be changed because of backward compatibility issues, but we still want to propose a "better" alternative. In that case, the old implementation can simply be deprecated.

A feature is marked as deprecated by adding a @deprecated phpdoc to relevant classes, methods, properties, ...:

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        /**
 * @deprecated since version 2.8, to be removed in 3.0. Use XXX instead.
 */
    

The deprecation message should indicate the version when the class/method was deprecated, the version when it will be removed, and whenever possible, how the feature was replaced.

A PHP E_USER_DEPRECATED error must also be triggered to help people with the migration starting one or two minor versions before the version where the feature will be removed (depending on the criticality of the removal):

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        @trigger_error('XXX() is deprecated since version 2.8 and will be removed in 3.0. Use XXX instead.', E_USER_DEPRECATED);
    

Without the @-silencing operator, users would need to opt-out from deprecation notices. Silencing swaps this behavior and allows users to opt-in when they are ready to cope with them (by adding a custom error handler like the one used by the Web Debug Toolbar or by the PHPUnit bridge).

When deprecating a whole class the trigger_error() call should be placed between the namespace and the use declarations, like in this example from ArrayParserCache:

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        namespace Symfony\Component\ExpressionLanguage\ParserCache;

@trigger_error('The '.__NAMESPACE__.'\ArrayParserCache class is deprecated since version 3.2 and will be removed in 4.0. Use the Symfony\Component\Cache\Adapter\ArrayAdapter class instead.', E_USER_DEPRECATED);

use Symfony\Component\ExpressionLanguage\ParsedExpression;

/**
 * @author Adrien Brault <adrien.brault@gmail.com>
 *
 * @deprecated ArrayParserCache class is deprecated since version 3.2 and will be removed in 4.0. Use the Symfony\Component\Cache\Adapter\ArrayAdapter class instead.
 */
class ArrayParserCache implements ParserCacheInterface
    

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.

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