PHP RFC: Deprecations for PHP 7.4

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

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
• is_writeable() function alias
• implode() parameter order mix
• convert_cyr_string() function
• money_format() function
• ezmlm_hash() function
• allow_url_include ini directive
• restore_include_path() function
• Unbinding $this from non-static closures

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 7.0 the dl() function is already only available on the CLI, CGI and Embed SAPIs. As such, it is already not available in typical web server SAPIs (FPM and Apache), where dl() may be disabled for security reasons. (TODO: CGI is a server SAPI, even if it's a bad one.)

Additionally the dl() function can also be disabled using the normal disable_functions mechanism, as such there is no need to have a separate ini option just for it.

Proposal: If the CLI, CGI or Embed SAPIs are used, emit a deprecation warning if enable_dl is non zero at start-up. In PHP 8 the option is removed and availability of dl() functionality is controlled only the SAPI.

Currently PHP has a float data type, with two additional aliases: double and real. The latter is 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: Emit a deprecation warning each time the (real) type-cast is used and mark is_real() as deprecated.

The hebrev() and hebrevc() functions helped display Hebrew on websites by converting logical Hebrew text to visual representation. Since the introduction of proper Unicode bidi support, this is no longer necessary. See W3C Visual vs. logical ordering of text for more information. As said there: “You should always create HTML (and any other type of markup) using logical ordering, and never use visual.” The legacy hebrev() functions violate this principle.

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

Proposal: Mark hebrev() or hebrevc() as deprecated.

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.

Proposal: Mark get_magic_quotes_gpc() and get_magic_quotes_runtime() as deprecated. This should only impact legacy code bases prior to PHP 5.4, running non-supported versions of PHP.

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 incorrect results may be returned for properties with integral keys.

Additionally, the fact that array_key_exists() accepts objects may mistakenly lead users to believe that it can operate on ArrayAccess objects in a sensible manner. This is not the case: array_key_exists() has no support for ArrayAccess, it exclusively works on mangled object properties.

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.

In PHP 7.3 add_slashes (FILTER_SANITIZE_ADD_SLASHES) was added as a new alias for this filter, to allow us to move away from the magic_quotes terminology.

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

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 emit 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: Remove this option without deprecation in PHP 8. On CLI $argv will always be available, on non-CLI it will never be available. Throwing a deprecation notice when $argv is used on non-CLI SAPIs is technically too involved to be worthwhile.

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 method 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.

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 the alias

The implode() function historically supports passing the $glue and $pieces parameters in reverse order from the documented order of arguments. However, this is inconsistent and the only function in the standard library which exhibits this behavior, and it should be amended.

This naturally also affects the implode() alias: join().

Proposal: Emit a deprecation warning if calling implode($pieces, $glue)

The convert_cyr_string() function allows conversion between cyrillic character sets. This is a legacy function back from when PHP didn't provide a lot of utility to convert between character sets. Today we have extensions like mbstring, intl, and iconv that allow this kind of conversion in a more general perspective. On top of this, this function also uses non-standard naming of character set names.

Proposal: Deprecate this function

The money_format() function allows currency based on locale-specific settings to be presented using the C function strfmon(). However some systems do not support this function, notably Windows. The functionality for formatting currency as provided by the intl extension should be used instead NumberFormatter::formatCurrency(). The intl extension also provides even further capabilities to parse currencies using NumberFormatter::parseCurrency() for any locale supported by ICU and not just the system which PHP is installed on.

Furthermore, the strfmon implementation seems to have an internal buffer overrun on macos, which indicates that this functionality is not well tested.

Proposal: Deprecate this function

The ezmlm_hash() function creates hashes of email addresses which the EZMLM/QMail email mailing list system understands. However, this function takes any input as long as it is a string, and doesn't care whether this is an email address or not and therefore can create possible hash collisions.

Besides that, the function is of limited usage for the average PHP developer given the EZMLM/QMail system is barely maintained and its last release was in 2007. The function was most likely added since the PHP.net infrastructure uses that for the mailing lists, however it can be implemented in userland code with ease for those still supporting this.

Proposal: Deprecate this function

The allow_url_include (disabled by default) ini directive allows the require, require_once, include and include_once language constructs to use url wrappers. To use this ini directive, the allow_url_fopen ini directive must also be enabled.

Setting this directive to on enables a potential security hazard if the path sent to either of the include constructs is crafted by external data. The ability to include a PHP file from a remote domain is questionable and has a huge potential security risk and therefore should be deprecated from PHP.

Proposal: Add a deprecation notice if allow_url_include=1 on startup

This function is essentially an “alias” of doing ini_restore('include_path'). The main rationale for this is to clean up the standard library for consistency, similar to what we have done with other functions that are just wrappers for ini directives.

Proposal: Deprecate the “alias” restore_include_path().

Currently it is possible to unbind the $this variable from a closure that originally had one by using $closure->bindTo(null). Due to the removal of static calls to non-static methods in PHP 8, we now have a guarantee that $this always exists inside non-static methods. We would like to have a similar guarantee that $this always exists for non-static closures declared inside non-static methods. Otherwise, we will end up imposing an unnecessary performance penalty either on $this accesses in general, or $this accesses inside such closures.

Proposal: Deprecate unbinding $this from a non-static closure declared inside a non-static method. A $this binding can be avoided in the first place by marking the closure as static.

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.