Description:
------------
Executing a prepared statement changes the type of bound parameters 
to string (Tested only with pgsql driver).

This bite me when I wanted to execute an insert statement only when 
the double value to be inserted actually changed, NULL being a 
possible value. Unfortunatly, comparing the new value with the old 
value with the !== operator didn't work, because the type-change 
made the test always evaluate to TRUE.


Reproduce code:
---------------
<?php
  $db = new PDO("pgsql:host=localhost dbname=test user=dummy");

  $db->query("CREATE TABLE test_table ( val REAL )");
  $qry = $db->prepare("INSERT INTO test_table VALUES (:val)");
  $qry->bindParam(":val",$bound_val);

  $bound_val = 5.2;
  echo "Type before execute(): ".gettype($bound_val)."\n";
  $qry->execute();
  echo "Type after execute(): ".gettype($bound_val)."\n";

  $db->query("DROP TABLE test");
?>

Expected result:
----------------
Type before execute(): double
Type after execute(): double


Actual result:
--------------
Type before execute(): double
Type after execute(): string