Description:
------------
The test script sums it up pretty well.  Basically, if I pass an array with a missing key to isset(), it's not supposed to throw an error.  After all, isset() is generally what people use for those kinds of sanity checks where unexpected data might be returned.

However, I just noticed (completely by accident) that, if you're passing an array with a set key followed by three or more missing keys to isset(), PHP will throw a fatal error and script execution will terminate at that point.

What's particularly strange about this is that it only seems to occur if the top-level array variable AND its first key are both set.  If I use the same depth on an undefined variable or on the defined array but with the top-level key being undefined, it works just fine.

In the example, this would mean that $non_existent_variable[...][...][...][...] is fine and $arr[0][...][...][...] is fine ($arr is defined but $arr[0] and $non_existent_variable are not).  However, if I do $arr["key"][...][...][...], where $arr["key"] is defined but the subsequent [...] keys are not, a fatal error is thrown.  That's clearly a bug.

In case anyone else encounters this before it's fixed, you can work around it by adding some additional (albeit cluttery) sanity checks.  For example, if your $arr["key"] is not an array and that's causing the error, simply add is_array( $arr["key"] ) to the ifcheck prior to isset and that will allow your script to proceed without dying.

I've already created a PHPT case for this.  It'd probably be a good idea to add it to run_tests, though I'm not entirely certain how/where to do that.

Looks like this bug was previously documented in 5.2.x (https://bugs.php.net/bug.php?id=44431), but it was closed with a comment saying that it had been fixed (or at least couldn't be repro'd) in 5.2.6.  So I'm guess either that person wasn't properly reproducing the conditions of the bug somehow or this is a regression.

Tested on Windows 7 x86_64 and CentOS 5.8 x86_64.  In both cases, PHP version was 5.3.15 (VC9 ZTS build on Windows).  Tested both via Apache/mod_php and CLI.  I have not tested this on 5.4 yet.  I don't have a 5.4 environment handy at the moment, so if somebody else could repro this on that version I'd be much obliged.  Thanks!

Test script:
---------------
<?php

$arr = array( "key" => "", 
		"key2" => array( "subkey" => array( "supersubkey" => array( "superdupersubkey" => "Hello." ) ) ), 
		"key3" => array( "subkey" => array( "supersubkey" => "Hello." ) ) );

if ( isset( $arr["key"]["non_existant_key"] ) )
{
	print "Arroooo?";
}

print "DEBUG #1.<br />\r\n";

$out = ( isset( $arr["key"]["non_existant_key"] ) ? "WTF?!" : NULL );

print "DEBUG #2.<br />\r\n";

foreach ( $arr as $key => $row )
{
	print ( isset( $row["subkey"]["supersubkey"] ) ? $row["subkey"]["supersubkey"] . "<br />\r\n" : NULL );
}

print "DEBUG #3.<br />\r\n";

if ( isset( $arr[0]["subkey"]["supersubkey"]["superdupersubkey"] ) )
{
	die( "Error : T_PAAMAYIM_NEKUDOTAYIM is too hard to pronounce!" );
}

print ( isset( $arr[0]["subkey"]["supersubkey"]["superdupersubkey"] ) ? "BAD-0<br />\r\n" : "OK-0<br />\r\n" );
print ( isset( $arr["key"]["subkey"]["supersubkey"]["superdupersubkey"] ) ? "BAD-1<br />\r\n" : "OK-1<br />\r\n" );
print ( isset( $arr["key2"]["subkey"]["supersubkey"]["superdupersubkey"] ) ? "OK-2<br />\r\n" : "BAD-2<br />\r\n" );
print ( isset( $arr["key3"]["subkey"]["supersubkey"]["superdupersubkey"] ) ? "BAD-3<br />\r\n" : "OK-3<br />\r\n" );

print "DEBUG #4.<br />\r\n";

foreach ( $arr as $key => $row )
{
	print ( isset( $row["subkey"]["supersubkey"]["superdupersubkey"] ) ? $row["subkey"]["supersubkey"]["superdupersubkey"] . "<br />\r\n" : NULL );
}

print "DEBUG #5.";

?>


Expected result:
----------------
DEBUG #1.<br />
DEBUG #2.<br />
Array<br />
Hello.<br />
DEBUG #3.<br />
OK<br />
OK-0<br />
OK-1<br />
OK-2<br />
OK-3<br />
DEBUG #4.<br />
Hello.<br />
DEBUG #5.


Actual result:
--------------
DEBUG #1.<br />
DEBUG #2.<br />
Array<br />
Hello.<br />
DEBUG #3.<br />
OK<br />
OK-0<br />
<br />
<b>Fatal error</b>:  Cannot use string offset as an array in <b>C:\Program Files (x86)\Apache2.2\htdocs\test8.php</b> on line <b>28</b><br />