Bug->Doc #52576 [Bgs->ReO]: Variable variables can create invalid variables.

Edit report at http://bugs.php.net/bug.php?id=52576&edit=1 ID: 52576 Updated by: rquadling@php.net Reported by: rquadling@php.net Summary: Variable variables can create invalid variables. -Status: Bogus +Status: Re-Opened -Type: Bug +Type: Documentation Problem -Package: Scripting Engine problem +Package: Documentation problem Operating System: Windows XP SP3 PHP Version: 5.3.3 Block user comment: N New Comment: If this is bogus in terms of the engine, then it is not bogus as a documentation problem. The documentation at http://docs.php.net/manual/en/language.variables.basics.php says that the following : "Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'" Clearly, [ and ] are NOT letters, numbers or underscores. Nor are any of the following characters ',.-+#*#+\ The comment was added 10 years ago (http://svn.php.net/viewvc/phpdoc/en/trunk/language/variables.xml?r1=16980&r2=22177), so in that time something changed. Using the ${$x} construct, you can create a variable of all 256 ASCII characters. <?php // Show all errors. error_reporting(-1); ini_set('display_errors', 1); // Initialize $ord = 0; $char = Null; $before = 0; $before = count($GLOBALS); foreach(range(0, 255) as $ord) { $char = chr($ord); ${$char} = $ord; } echo 'Created ', (count($GLOBALS) - $before), ' variables.', PHP_EOL; ?> outputs ... Created 256 variables. From my testing of PHP3.0.11 through to the latest V5.3.4-dev, the output is the same. A variable can start with anything if using the ${$a} mechanism. Previous Comments: ------------------------------------------------------------------------ [2010-08-10 19:46:09] johannes@php.net Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php Variable names may contain any character. ${',.-+#*#+\\'} = 42; This is expected. ------------------------------------------------------------------------ [2010-08-10 18:21:13] rquadling@php.net Description: ------------ It seems you can create a variable in $GLOBALS that is not accessible as a normal variable. I found this because I wanted to use variable variables to populate a nested array. Jim Lucas, in http://news.php.net/php.general/307392, comments that the use of eval() may be appropriate in the case. That aside, the entry that is created in $GLOBALS doesn't follow the rules for variable naming in http://docs.php.net/manual/en/language.variables.basics.php, namely that '[' and ']' are not valid variable names. I think this should have t least produced an E_WARNING. So, with all of that, I'm not sure if this is a bug or a documentation problem. I certainly think it is an edge case. Regards, Richard Quadling. Test script: --------------- <?php // Show all errors. error_reporting(-1); ini_set('display_errors', 1); // Expectation was to be able to create a deep array using variable variables. $a = 'b[1][2][3]'; $$a = 'Inaccessible?'; print_r($b); // Hide superglobals unset($_POST); unset($_GET); unset($_SESSION); unset($_FILES); unset($_COOKIE); unset($_SERVER); unset($argv); unset($argc); // Reveals inaccessible variable. var_dump($GLOBALS); Expected result: ---------------- Array ( [1] => Array ( [2] => Array ( [3] => Inaccessible? ) ) ) array(3) { ["GLOBALS"]=> *RECURSION* ["a"]=> string(10) "b[1][2][3]" ["b"]=> array(1) { [1]=> array(1) { [2]=> array(1) { [3]=> string(13) "Inaccessible?" } } } } Actual result: -------------- Notice: Undefined variable: b in - on line 5 array(4) { ["GLOBALS"]=> *RECURSION* ["a"]=> string(10) "b[1][2][3]" ["b[1][2][3]"]=> string(13) "Inaccessible?" ["php_errormsg"]=> string(21) "Undefined variable: b" } ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=52576&edit=1