This RFC is to discuss comparison and conversion inconsistencies in PHP.
There are number of in comparison and conversion inconsistencies.
For example,
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.
Type juggling only works for INTEGER or HEX like strings.
Most problematic is HEX like strings being auto-coerced during comparison, but using different rules from manual casting. That is, ( 0x0A == “0x0A” ) is not treated as ( 0x0A == (int)“0x0A” ), although “0x0A” is translated to a number.
This despite http://us2.php.net/manual/en/language.operators.comparison.php, which states clearly that for number-string comparison, we “Translate strings and resources to numbers.” While it is feasible that some string patterns cannot be “translated” (OCTAL and BINARY) at all, once a “translation” is attempted, it should follow the same rules as (int) casting for the same string. It is hard to view it is anything but a bug that it does not.
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"
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)
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)
Null string is not handled as ARRAY.
https://github.com/php/php-src/pull/463
Test script:
$a = ''; // empty string $a[10] = 'a'; echo $a; // "Array" $b = ' '; // non empty string $b[10] = 'b'; echo $b; // " b"
Expected result:
" a" " b"
Actual result:
"Array" " b"
PHP converts “integer like string to integer”.
<?php
// this is the problem, which we'd expect
// to return false, but which returns true:
echo (2 == '2b').'<br />';
// this is probably what's happening:
echo (2 == intval('2b')).'<br />';
// this is what probably should happen:
echo (strval(2) != '2b').'<br />';
?>
https://bugs.php.net/bug.php?id=66211
Not only is this not a bug, it isn't even exceptional behavior on the modern web. Users who find this behavior surprising are likely inexperienced with MySQL -- clearly PHP's partner in server-side ubiquity as part of the dominant *AMP stack -- which has the exact same rules for auto-coercion of “numeroalphabetic” strings in a comparison context.
In MySQL (all supported versions):
SELECT CASE WHEN '-45herearesomeletters' = -45 THEN 'true' ELSE 'false' END
prints 'true'
There are other popular languages that follow the same casting/coercion rule, though they do not automatically perform the coercion during comparison. For example, JavaScript parseInt('-45herearesomeletters') results in the integer -45. In SQLite, the ubiquitous embedded SQL database, also CAST( '-45herearesomeletters' AS SIGNED ) produces the integer -45.
The SQLite documentation explains the logic well:
When casting a TEXT value to INTEGER, the longest possible prefix of
the value that can be interpreted as an integer number is extracted
from the TEXT value and the remainder ignored. Any leading spaces in
the TEXT value when converting from TEXT to INTEGER are ignored. If
there is no prefix that can be interpreted as an integer number, the
result of the conversion is 0. (http://www.sqlite.org/lang_expr.html#castexpr)
And this behavior is not considered particularly “distinctive”. (http://sqlite.org/different.html)
Since the ubiquity of MySQL has been used to support the expectations users should have of PHP, it's fair to note Oracle, SQL Server, and PostgreSQL will not allow the above comparison to be performed: the statement produces a fatal error. It's a runtime casting error: these languages do not prohibit comparing values of different datatypes, as long as the engine can cast the runtime contents of the value. Yet such implementations, arguably, violate the “least astonishment” concept, since a errant letter modifier like '1A' will cause a fatal error where the expectation might be to either have a '1A' compare equal to 1 (as in MySQL) or fail gracefully (as in SQLite). In this respect, the SQLite behavior is more balanced than that of Oracle/MSSQL/PGSQL, and PHP and MySQL's behavior is graceful, generous, and reasonable.
With PHP and MySQL agreeing on this behavior, it is clear that automatically coercing a “numeroalphabetic” string (for want of a better term) to a number via truncation is common practice on the web, even if it is news to the inexperienced user.
String decrements is inconsistent
NAN/INF issue.
$f = NAN; var_dump(++$f); // float NAN var_dump((float) NAN); // float NAN var_dump((int) NAN); // int -2147483648 -> what? var_dump((bool) NAN); // bool true -> makes sense $f = INF; var_dump(++$f); // float INF var_dump((float) INF); // float INF var_dump((int) INF); // int 0 -> what? var_dump((bool) INF); // bool true -> so why int 0? var_dump((int) (bool) INF); // int 1
E_WARNING for these invalid/unreliable operations might be better.
This could be mitigated by GMP float support.
Object/Array cast looses accessibility of numeric property/element. https://bugs.php.net/bug.php?id=66173
$ php -v
PHP 5.5.7 (cli) (built: Dec 11 2013 07:51:06)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies
$ php -r '$obj = new StdClass; $obj->{12} = 234; ${1} = 567; var_dump($obj, ${1}); $ary = (array)$obj; var_dump($ary, $ary[12]);'
object(stdClass)#1 (1) {
["12"]=>
int(234)
}
int(567)
Notice: Undefined offset: 12 in Command line code on line 1
array(1) {
["12"]=>
int(234)
}
NULL <= SHOULD BE int(234)
assert() does not accept closure while it accepts functions.
php > function f() {return FALSE;}
php > assert(f());
Warning: assert(): Assertion failed in php shell code on line 1
php > assert(function() {return FALSE;});
https://bugs.php.net/bug.php?id=66682
var_dump(filter_var('01', FILTER_VALIDATE_INT)); var_dump(filter_var('01', FILTER_VALIDATE_FLOAT));
bool(false) double(1)
https://bugs.php.net/bug.php?id=53104
This is not a bug. If one of operand is BOOL(or NULL), both operands are converted to BOOL and evaluated as BOOL. It may be good idea that document this behavior in min() manual.
Status Documented.
If not all, almost all functions return NULL when required function parameter is missing or wrong type. However, almost all functions return FALSE when they have errors.
The manual has document for this behavior http://www.php.net/manual/en/functions.internal.php
Note: If the parameters given to a function are not what it expects, such as passing an array where a string is expected, the return value of the function is undefined. In this case it will likely return NULL but this is just a convention, and cannot be relied upon.
This behavior could be cause of bug in scripts. For instance,
if (FALSE === some_func($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
Bug reports are not verified carefully. Removing wrong one, adding proper one is appreciated.
Not yet.
Not yet.
PHP 6.0 probably.
Not yet.
Not yet.
If there are any php.ini settings then list:
Not yet.
Make sure there are no open issues when the vote starts!
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.
This sections details areas where the feature might be improved in future, but that are not currently proposed in this RFC.
Include these so readers know where you are heading and can discuss the proposed voting options.
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.
After the project is implemented, this section should contain
Links to external references, discussions or RFCs
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