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The following class (code) causes a segmentation fault if it has the ROLLBACK query in the destructor.
It results in a segfault always if it's executed as a command line script, and sometimes if it's called by a web request (lots of calls repeteadly and with persistence).
The extension code (pgsql.c) has a "feature" which automatically close every query result that was left opened. But I think that it's pretty acceptable to have a script like this one.
<?
class db
{
        public function __construct($string)
        {
                $this->handle = pg_pconnect($string);
                $this->Execute('BEGIN');
        }

        public function Commit()
        {
                $this->execute('COMMIT');
                $this->execute('BEGIN');
        }

        public function Execute($query)
        {
                $res = pg_query($this->handle, $query);
                pg_affected_rows($res);
                pg_free_result($res);
        }

        public function __destruct()
        {
                $this->execute('ROLLBACK');
                pg_close($this->handle);
        }

        private $handle;
}

$c = new db([connection string]);
$c->execute("SELECT 1");
$c->Commit();
?>

Please try using this CVS snapshot:

  http://snaps.php.net/php5-STABLE-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php5.0-win32-latest.zip

same result...

Thank you for this bug report. To properly diagnose the problem, we
need a backtrace to see what is happening behind the scenes. To
find out how to generate a backtrace, please read
http://bugs.php.net/bugs-generating-backtrace.php

Once you have generated a backtrace, please submit it to this bug
report and change the status back to "Open". Thank you for helping
us make PHP better.

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

Same problem under php 5.0.4 and postgres 8.0.2.
Sample code,who causes segfault:

class db
{
function connect(){
$this->db = pg_connect($this->conn);
 if (!$this->db) {
	$this->ErrorMsg('cannot connect to db');
	}
}

function ErrorMsg($ErrDescription)
	{
		$this->sql("ROLLBACK"); /* if this line commented,all going OK */
		$this->disconnect();
		die("Error<br>$ErrDescription");
	}
}

Sorry for the lack of feedback. Since the bug can be ommited by removing the rollback statement from the destructor, i don't have the time to do further tests.