fixed a warning and the return key submits the form properly now.

src/addrbook_search.php

@@ -140,6 +140,7 @@ displayHtmlHeader();
 /* Initialize vars */
 if (!isset($query)) { $query = ''; }
 if (!isset($show))  { $show  = ''; }
+if (!isset($backend)) { $backend = ''; }
 
 /* Choose correct colors for top and bottom frame */
 if ($show == 'form' && !isset($listall)) {
@@ -166,7 +167,7 @@ $abook = addressbook_init();
 
 /* Create search form */
 if ($show == 'form' && empty($listall)) {
-    echo '<FORM NAME=sform TARGET=abookres ACTION="' . $PHP_SELF .
+    echo '<FORM NAME=sform TARGET=abookres ACTION="addrbook_search.php'. 
          '" METHOD="POST">' . "\n" .
          '<TABLE BORDER="0" WIDTH="100%" HEIGHT="100%">' .
          '<TR><TD NOWRAP VALIGN=middle align=left width=10%>' . "\n" .