Edit report at http://bugs.php.net/bug.php?id=53971&edit=1
ID: 53971 Updated by: dtajchre...@php.net Reported by: david at frankieandshadow dot com Summary: isset() and empty() produce apparently spurious runtime error -Status: Bogus +Status: Open Type: Bug Package: Arrays related Operating System: Linux, Redhat Enterprise PHP Version: 5.3.5 Block user comment: N Private report: N New Comment: It looks like there was the change in behavior between 5.2.9 and 5.2.10. I don't know whether this was intentional or a side affect of another change. The difference can be seen here: http://codepad.org/iYcCCAkA /* 5.2.5 */ http://codepad.viper-7.com/msAbwQ /* 5.2.15RC3-dev */ I've reopened the ticket so this can be discussed. If it is intentional, it needs to be documented. Previous Comments: ------------------------------------------------------------------------ [2011-02-09 21:30:10] david at frankieandshadow dot com I appreciate that this is the case. When you say "$obj->m[0] doesn't exist", yes I agree, BUT that is what the isset is testing for. If it SHOULD produce a runtime error, then (a) this is a very subtle non-upwards compatible change from 5.2, and (b) the example I quoted does NOT produce a runtime error so is a bug. (And producing a runtime error in these circumstances is terribly inconvenient, it means you can't test existence in one go but have to try each element individually). If it SHOULD NOT produce a runtime error then there is a problem with the larger code I have which follows this pattern and is doing so. There is a bug here one way or the other: either my larger program is wrong (but has worked for years with this code in it) or the example I put in the bug report is wrong in that it does not produce an error and never has. At present the behaviour is inconsistent. ------------------------------------------------------------------------ [2011-02-09 17:50:29] dtajchre...@php.net $obj->m is an empty string. You try to access a non-integer offset. Non-integer offsets are converted to integers. So in other words: $obj->m['a'] becomes $obj->m[0] $obj->m is an empty string and $obj->m[0] doesn't exist This behavior is documented here: http://us.php.net/manual/en/language.types.string.php "Warning Writing to an out of range offset pads the string with spaces. Non-integer types are converted to integer. Illegal offset type emits E_NOTICE. Negative offset emits E_NOTICE in write but reads empty string. Only the first character of an assigned string is used. Assigning empty string assigns NUL byte." Simplifying the problem: http://codepad.org/G31wr4oJ ------------------------------------------------------------------------ [2011-02-09 13:12:44] david at frankieandshadow dot com Description: ------------ First, apologies, this is 5.3.3. I have no means of upgrading to check whether this is a fixed issue. I can't see anything similar in the bug database. An expression of the form isset($obj->m['a']['b']) produces a runtime error when m is not actually an array but a zero length string: Uninitialized string offset: 0 The same is the case if I use empty instead of isset. The same code worked in 5.2. Changing it to isset($obj->m['a']) && isset($obj->m['a']['b']) works. isset is not supposed to produce any runtime error, surely, in this kind of use. The object member values arise from a database lookup, and normally the field (m above) will be a serialized array in the database, but the first time the database column will be empty, leading to an empty string assignment to m. In addition once populated the object is stored in $_SESSION (actually in $_SESSION['p']['q']) and then $obj is obtained by assignment from the session, like this $session =& $_SESSION['p']; // where $_SESSION['p'] is set in a previous page // populate new $obj1 from database $session['q'] = $obj1; ... $obj =& $session['q']; and the offending code is then executed elsewhere some time later. However, abstracting the code from this much bigger program does not demonstrate the problem, which suggests to me something is corrupted somewhere. This is what I tried on its own, which is as close as I can reasonably get to the situation here, but it works. (The =& are leftovers from what was originally a PHP4 app; I know all objects are assigned by reference in PHP5). class c { var $m; } session_start(); if (! isset($_SESSION['p'])) { $_SESSION['p'] = array(); echo "set session array"; exit; } $session =& $_SESSION['p']; $obj1 = new c(); $obj1->m = ''; $session['q'] = $obj1; $obj =& $session['q']; function check() { global $obj; echo (isset($obj->m['a']['b']) ? 'Yes' : 'No'); } check(); Expected result: ---------------- isset to return FALSE Actual result: -------------- runtime error Uninitialized string offset: 0 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=53971&edit=1