PHP RFC: Deprecations for PHP 7.4

• Date: 26th June, 2018
• Authors: Kalle Sommer Nielsen kalle@php.net, Nikita Popov nikic@php.net
• Status: In Draft

This is a draft RFC for multiple deprecations targeting PHP 7.4. The RFC proposes to deprecate the listed functionality in PHP 7.4 and remove it in PHP 8.

The following list provides a short overview of the functionality targeted for deprecation, while more detailed explanation is provided in the Proposal section:

• enable_dl php.ini directive
• The 'real' type
• The hebrev() & hebrevc() functions
• Magic quotes legacy
• array_key_exists() with objects
• FILTER_SANITIZE_MAGIC_QUOTES filter
• INPUT_SESSION & INPUT_REQUEST input types for the filter extension
• apache_request_headers() function
• register_argc_argv ini directive
• Reflection export() methods
• mb_strrpos() with encoding as 3rd argument
• __CLASS__ constant
• get_called_class() function
• is_writeable() function alias

The following are still Work-In-Progress and ideas:

• Second parameter of spl_autoload() and its associated function spl_autoload_extensions()
• convert_cyr_string()
• allow_url_include ini directive
• Unify parameter order for implode() to match explode()
• Function variants that already exists as constants (e.g. php_sapi_name(), phpversion(), pi())
• money_format()
• ezmlm_hash()

Each feature proposed for deprecation is voted separately. Each vote requires a 2/3 majority, independently of whether it is a language or standard library change. All votes refer to deprecation in PHP 7.4 and removal in PHP 8.0.

The enable_dl php.ini directive controls whether or not the dl() function is available. However as of PHP 5.3, the dl() function was limited to the CLI and Embed SAPIs and between PHP 5.3.9 and 7.0.0, it was also available in the FPM SAPI.

This means that the enable_dl effectively has no greater meaning as it will never be available in a shared environment anyway, as any CLI user could easily bypass it anyway.

Proposal: Add a deprecation warning if enable_dl is non zero at start-up and when using CLI or Embed.

Currently PHP has a float data type, with 2 additional aliases: double & real. The latter is very very rarely used and should be deprecated. This includes both the (real) type-cast and the is_real() function. Currently the settype() function does not support the 'real' string, so it is not affected.

Upgrading is relatively easy and can be done by replacing all (real) type-casts with (float) and all is_real() calls with is_float().

Proposal: Add a deprecation warning for each time the (real) type-cast is used and each time the is_real() function is called.

The hebrev() and hebrevc() functions are functions that helped make websites hebrew before browsers properly supported RTL, by simply converting the nature of RTL to LTR writing for easier display on websites. All modern browsers nowadays properly support unicode and RTL text direction and therefore it seems reasonable to deprecate these functions.

The hebrevc() function is essentially the same as calling nl2br() on the result of a hebrev() call.

Proposal: Add a deprecation warning if either hebrev() or hebrevc() is called.

PHP's infamous magic_quotes configuration was removed in PHP 5.4 and the function implementations of checking whether or not these settings have been enabled have returned false since then. With PHP 7.0 not having magic_quotes at all, it is time to deprecate these functions and remove them entirely.

This should effectively only hit legacy code bases prior to PHP 5.4, which is running non supported versions of PHP.

Proposal: Add a deprecation warning if either get_magic_quotes_gpc() or get_magic_quotes_runtime() is called.

The documentation already marks the use of array_key_exists() with objects as legacy behavior:

For backward compatibility reasons, array_key_exists() will also return TRUE if key is a property defined within an object given as array. This behaviour should not be relied upon, and care should be taken to ensure that array is an array. To check whether a property exists in an object, use property_exists().

array_key_exists() on objects also has some technical issues: It operates directly on mangled property names and does not respect property visibility. Furthermore it does not take into account differences in normalization between array and object keys, so that incorrect results may be returned for properties with integral keys.

Proposal: Throw a deprecation warning if an object is passed to array_key_exists().

Magic quotes were deprecated all the way back in PHP 5.3 and later removed in PHP 5.4. The filter extension implements a sanitization filter that mimics this behavior of magic_quotes by calling addslashes() on the input in question.

As of PHP 7.3, a new alias of this filter was added add_slashes (FILTER_SANITIZE_ADD_SLASHES) to help ease the migration and allow us to move away from the magic_quotes name as calling addslashes() can still potentially be useful.

Proposed action: Emit a deprecation notice each time the FILTER_SANITIZE_MAGIC_QUOTES filter is used and advice users to use the add_slashes (FILTER_SANITIZE_ADD_SLASHES) filter.

The filter extension implements a set of INPUT_XXX constants for telling the source of where the input is coming from. However, the INPUT_SESSION and INPUT_REQUEST inputs were never implemented but their constants are and simply just emits an E_WARNING when used.

Impact: Minimal as they do not serve any function and functionality relying on this is broken (non functional).

Proposed action: Keep the E_WARNING and mention that these will be removed in a future version of PHP.

This function with an Apache-specific name is also available in other SAPIs, even though it is also available under the SAPI-independent name getallheaders(). The SAPI-specific function should be removed in favor of the more general one.

Proposed action: Mark apache_request_headers() as deprecated.

This ini setting controls whether the $argv and $argc variables are registered. On CLI SAPIs these contain the CLI arguments, on non-CLI SAPIs they contain the GET string parsed as if it were CLI arguments.

On CLI SAPIs register_argc_argv=1 is a “hardcoded” ini setting, which means that it cannot be disabled through php.ini, it may only be overridden on the command line using -d register_argc_argv=0. For other SAPIs this ini setting also defaults to on, but both php.ini-development and php.ini-production disable it.

This ini setting should be removed for two reasons: On CLI SAPIs it is a liability, which prevents us from strictly guaranteeing the availability of $argv. On non-CLI SAPIs this functionality seems to be of questionable usefulness, while also negatively impacting performance and perpetuating questionable security practices.

Proposed action: Unclear. We could generate a deprecation notice if this setting is enabled on non-CLI SAPIs, however that would make the default behavior generate a deprecation notice. It might be possible to also change the default behavior at the same time.

The Reflector interface, which is implemented by all reflection classes, specifies two methods: __toString() and export(). The latter is a static method which, ostensibly, does not accept arguments. In reality this static methods is implemented with varying signatures in each subclass, something which would normally result in an incompatible signature error. However, the implementation uses an internal mechanism to suppress this error.

The export() methods are essentially equivalent to a combination of the class constructor and __toString(). For example:

ReflectionFunction::export('foo');
// same as
echo new ReflectionFunction('foo'), "\n";
 
$str = ReflectionFunction::export('foo', true);
// same as
$str = (string) new ReflectionFunction('foo');

As such, the export() method is wholly unnecessary, confusing, and violates PHP's own inheritance rules.

Proposed action: In PHP 7.4 remove the method from the Reflector interface and deprecate all implementations of the method in reflection classes. In PHP 8 also remove the implementations.

The documentation for mb_strrpos() states:

The encoding parameter was moved from the third position to the fourth in PHP 5.2.0. For backward compatibility, encoding can be specified as the third parameter, but doing so is deprecated and will be removed in the future.

However, this deprecation has never been realized in the implementation. The need to support both signatures makes this parameter behave subtly different from other integer parameters (e.g. it is not subject to strict types). As little software is expected to support both PHP 7.4 and PHP 5.1, enforcing the new signature does not pose a significant backwards compatibility concern.

Proposed action: In PHP 7.4 throw a deprecation warning if an encoding is passed as the 3rd argument. In PHP 8 change the argument to accept an integer.

This constant is the old way of detecting current class name.

Since PHP 5.5, __CLASS__ is equivalent to self::class.

Proposal: Deprecate __CLASS__ constant in favor of self::class.

This function is the old way of detecting current class name during LSB.

Since PHP 5.5, using get_called_class() is equivalent to static::class.

Proposal: Deprecate get_called_class() in favor of static::class.

The is_writeable() function is an alias of is_writable(). is_writeable() is notorious in the sense that it has a spelling mistake in its name and since the introduction of is_writable() been considered soft deprecated.

Proposal: Deprecate alias

For PHP 7.4 additional deprecation notices will appear. For PHP 8.0 the previously deprecated functionality will no longer be available.

Each of the bullet points above will get a separate vote. All votes will require a 2/3 supermajority, independently of whether they are language changes or not.

1. 2018-07-05: Added __CLASS__, get_called_class() and array_key_exists() with object arg (majkl)