Description:
------------
When mysqli or/and tidy extensions are loaded, they produce a memory error and make the server (Apache 2.2.2) crashes.

So far I know these problems should have been introduced in the 5.1.3 or 5.1.4 because i ran long with 5.1.2 without noticing any of those problems.

Reproduce code:
---------------
<?
// only one test is necessary
// test 1
function test() { test(); }
test();

// test 2
class a {
 function test() { $this->test(); }
};
$a=new a();
$a->test();
?>

Expected result:
----------------
Without those extensions loaded, you get a blank file to download, which is the correct result.

Actual result:
--------------
With one or both of those extensions loaded, you get a crash of the server, even when using none of the extension's functionality (see the code above).

Another complete crash appears in the export function of phpMyAdmin (export a table in sql for example), I didn't parsed that code for the moment, but it appears even with only mysql (not i) extension loaded.