PHP: rfc:comparison_inconsistency

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====== PHP RFC: Existing comparison and conversion inconsistency  ======
  * Version: 0.1
  * Date: 2013-10-31
  * Author: Yasuo Ohgaki <yohgaki@php.net>
  * Status: Draft (or Under Discussion or Accepted or Declined)
  * First Published at: http://wiki.php.net/rfc/comparison_inconsistency

This RFC is to discuss comparison and conversion inconsistencies in PHP. 

===== Introduction =====

There are number of in comparison and conversion inconsistencies.

For example, 
  * https://bugs.php.net/bug.php?id=53104 reports comparison inconsistency in min() function.

There are number issues of like this.

Purpose of this RFC is fix inconsistency where it's feasible, otherwise document then fully if it's not documented already.

===== Inconsistency =====
==== Conversion/comparison ====

Type juggling only works for INTEGER or HEX like strings.

=== HEX ===
Code
  var_dump(0x0A);
  var_dump("0x0A");
  var_dump((int)"0x0A");
  var_dump((float)"0x0A");
  var_dump(intval("0x0A"));
  var_dump(floatval("0x0A"));

Output
  int(10)
  string(4) "0x0A"
  int(0)
  float(0)
  int(0)
  float(0)

Code
  if (0x0A == '0x0A') {
    echo "0x0A == '0x0A'".PHP_EOL;
  }
  if (0x0A == "0x0A") {
    echo '0x0A == "0x0A"'.PHP_EOL;
  }

Output
  0x0A == '0x0A'
  0x0A == "0x0A"


=== Octal ===

Code
  var_dump(010);
  var_dump("010");
  var_dump((int)"010");
  var_dump((float)"010");
  var_dump(intval("010"));
  var_dump(floatval("010"));

Output
  int(8)
  string(3) "010"
  int(10)
  float(10)
  int(10)
  float(10)

CODE
  if (010 == '010') {
    echo "010 == '010'".PHP_EOL;
  }
  if (010 == "010") {
    echo '010 == "010"'.PHP_EOL;
  }

OUTPUT
  (NONE)


=== BINARY ===

Code
  var_dump(0b110);
  var_dump("0b110");
  var_dump((int)"0b110");
  var_dump((float)"0b110");
  var_dump(intval("0b110"));
  var_dump(floatval("0b110"));

Output
  int(6)
  string(5) "0b110"
  int(0)
  float(0)
  int(0)
  float(0)

CODE
  if (0b010 == '0b010') {
    echo "0b010 == '0b010'".PHP_EOL;
  }
  if (0b010 == "0b010") {
    echo '010 == "010"'.PHP_EOL;
  }

OUTPUT
  (NONE)

==== Function/Method ====

=== min() function ===

https://bugs.php.net/bug.php?id=53104

This is not a bug. If one of operand is BOOL(or NULL), both operands are converted to BOOL and evaluated as BOOL. It may be good idea that document this behavior in min() manual.

=== Return value of wrong internal function/method parameters ===

If not all, almost all functions return NULL when required function parameter is missing or wrong type. However, almost all functions return FALSE when they have errors.

The manual has document for this behavior
http://www.php.net/manual/en/functions.internal.php

  Note: If the parameters given to a function are not what it expects, such as passing an array 
  where a string is expected, the return value of the function is undefined. In this case it will 
  likely return NULL but this is just a convention, and cannot be relied upon.

This behavior could be cause of bug in scripts. For instance,

  if (FALSE === some_func($wrong_parameter)) {
     // Error happend!
  } else {
     // OK to go
  }

Users should not rely on return value as it may return NULL for wrong parameters. Users should rely on error/exception handler for such case as internal functions raise E_WARNING in this case. (If there are function that does not raise error, it is subject to be fixed.)

It may be good to add use of error/exception handler as best practice in the manual.
http://www.php.net/manual/en/functions.internal.php

There are bug reports that complain return value inconsistency. The document could be improved with more explanations.

== Related Bug Reports ==
  * https://bugs.php.net/bug.php?id=60338 (Returns value for wrong key())
  * https://bugs.php.net/bug.php?id=64860 (returns NULL for wrong file parameter)
  * https://bugs.php.net/bug.php?id=65986 (returns NULL for wrong parameter)
  * https://bugs.php.net/bug.php?id=65604 (returns NULL for too huge parameter, probably)
  * https://bugs.php.net/bug.php?id=59225 (returns NULL when it should return FALSE? when server is not accessible?)
  * https://bugs.php.net/bug.php?id=65910 (returns NULL for wrong parameter)
  * https://bugs.php.net/bug.php?id=62492 (returns NULL for wrong parameter)
  * https://bugs.php.net/bug.php?id=44049 (returns NULL for wrong parameter by mistake? Expecting prepared query params?)
  * https://bugs.php.net/bug.php?id=64140 (returns NULL for wrong parameter without error/exception?)

Bug reports are not verified carefully. Removing wrong one, adding proper one is appreciated.

== Developer Guideline ==

  * Internal function/method should raise error(or exception) for invalid parameters. (parse parameters function does this)
  * Internal function/method is better to return NULL for invalid parameters as most functions do.
  * Internal function/method is better to return FALSE for other errors.

== User Guideline ==

  * User should not rely return value only for failure condition, but should rely error/exception handler for failure also.

===== Proposal =====

Not yet.

===== Backward Incompatible Changes =====

Not yet.

===== Proposed PHP Version(s) =====

PHP 6.0 probably.

===== Impact to Existing Extensions =====

Not yet.

===== New Constants =====

Not yet.

===== php.ini Defaults =====

If there are any php.ini settings then list:
  * hardcoded default values
  * php.ini-development values
  * php.ini-production values

Not yet.

===== Open Issues =====

Make sure there are no open issues when the vote starts!

===== Unaffected PHP Functionality =====

List existing areas/features of PHP that will not be changed by the RFC.

This helps avoid any ambiguity, shows that you have thought deeply about the RFC's impact, and helps reduces mail list noise.

===== Future Scope =====

This sections details areas where the feature might be improved in future, but that are not currently proposed in this RFC.

===== Proposed Voting Choices =====

Include these so readers know where you are heading and can discuss the proposed voting options.

===== Patches and Tests =====

Links to any external patches and tests go here.

If there is no patch, make it clear who will create a patch, or whether a volunteer to help with implementation is needed.

Make it clear if the patch is intended to be the final patch, or is just a prototype.

===== Implementation =====

After the project is implemented, this section should contain 
  - the version(s) it was merged to
  - a link to the git commit(s)
  - a link to the PHP manual entry for the feature

===== References =====

Links to external references, discussions or RFCs

===== Rejected Features =====

Keep this updated with features that were discussed on the mail lists.

===== ChangeLog =====

  * 2013/10/31 - Initial version.
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