Bug 1766 fixed : [PostgreSQL] unkown database function UNIX_TIMESTAMP()

Add a new function pwg_db_date_to_ts() to calculate a timestamp from a date
Merge from trunk

git-svn-id: http://piwigo.org/svn/branches/2.1@6667 68402e56-0260-453c-a942-63ccdbb3a9ee

include/dblayer/functions_mysql.inc.php

@@ -636,6 +636,11 @@ function pwg_db_get_weekday($date)
   return 'WEEKDAY('.$date.')';
 }
 
+function pwg_db_date_to_ts($date) 
+{
+  return 'UNIX_TIMESTAMP('.$date.')';
+}
+
 // my_error returns (or send to standard output) the message concerning the
 // error occured for the last mysql query.
 function my_error($header, $die)

include/dblayer/functions_pdo-sqlite.inc.php

@@ -550,6 +550,11 @@ function pwg_db_get_weekday($date)
   return 'strftime(\'%w\',date('.$date.',\'-1 DAY\'))';
 }
 
+function pwg_db_date_to_ts($date) 
+{
+  return 'UNIX_TIMESTAMP('.$date.')';
+}
+
 // my_error returns (or send to standard output) the message concerning the
 // error occured for the last mysql query.
 function my_error($header, $die)

include/dblayer/functions_pgsql.inc.php

@@ -596,6 +596,11 @@ function pwg_db_get_weekday($date)
   return 'EXTRACT(ISODOW FROM '.$date.')::INTEGER - 1';
 }
 
+function pwg_db_date_to_ts($date) 
+{
+  return 'EXTRACT(EPOCH FROM '.$date.')';
+}
+
 // my_error returns (or send to standard output) the message concerning the
 // error occured for the last pgsql query.
 function my_error($header, $die)

include/dblayer/functions_sqlite.inc.php

@@ -561,6 +561,11 @@ function pwg_db_get_weekday($date)
   return 'strftime(\'%w\',date('.$date.',\'-1 DAY\'))';
 }
 
+function pwg_db_date_to_ts($date) 
+{
+  return 'UNIX_TIMESTAMP('.$date.')';
+}
+
 // my_error returns (or send to standard output) the message concerning the
 // error occured for the last mysql query.
 function my_error($header, $die)

include/functions_session.inc.php

@@ -175,7 +175,7 @@ function pwg_session_gc()
   $query = '
 DELETE
   FROM '.SESSIONS_TABLE.'
-  WHERE UNIX_TIMESTAMP(NOW()) - UNIX_TIMESTAMP(expiration) > '
+  WHERE '.pwg_db_date_to_ts('NOW()').' - '.pwg_db_date_to_ts('expiration').' > '
   .$conf['session_length'].'
 ;';
   pwg_query($query);