(PHP 4 >= 4.0.1, PHP 5)
pg_trace — Enable tracing a PostgreSQL connection
$pathname
   [, string $mode = "w"
   [, resource $connection
  ]] )pg_trace() enables tracing of the PostgreSQL frontend/backend communication to a file. To fully understand the results, one needs to be familiar with the internals of PostgreSQL communication protocol.
For those who are not, it can still be useful for tracing errors in queries sent to the server, you could do for example grep '^To backend' trace.log and see what queries actually were sent to the PostgreSQL server. For more information, refer to the » PostgreSQL Documentation.
pathnameThe full path and file name of the file in which to write the trace log. Same as in fopen().
modeAn optional file access mode, same as for fopen().
connection
       PostgreSQL database connection resource.  When 
       connection is not present, the default connection 
       is used. The default connection is the last connection made by 
       pg_connect() or pg_pconnect().
      
   Returns TRUE on success or FALSE on failure.
  
Example #1 pg_trace() example
<?php
$pgsql_conn = pg_connect("dbname=mark host=localhost");
if ($pgsql_conn) {
   pg_trace('/tmp/trace.log', 'w', $pgsql_conn);
   pg_query("SELECT 1");
   pg_untrace($pgsql_conn);
   // Now /tmp/trace.log will contain backend communication
} else {
   print pg_last_error($pgsql_conn);
   exit;
}
?>