View as custom / Link to another table

I have this field set as text but view as custom with php runner 9.7 . Basically you would click on the link in one table and it would go to another table Book_Display_add.php table with the values already filled in . This worked with php 5.2. My server just got upgraded to php 5.6 and now I get the error below. I am stuck here .
view as custom:
$value ="<a href='Book_Display_add.php?fldcategory=".$data["fldcategory"]."&fldavail=".$data["Pos"]."'>BOOK HERE</a>"; // dosen't work with php5.6 version. did something change in my code that is deprecated
Fatal error: Call to a member function gSQLWhere() on null in C:\Inetpub\vhosts\mywebsite\httpdocs\proformsd\include\Book_Display_variables.php on line 18
This is the variables.php file
$strTableName="Book_Display";

$_SESSION["OwnerID"] = $SESSION["".$strTableName."_OwnerID"];
$strOriginalTableName="Book_Display";
$gstrOrderBy="ORDER BY orderdate DESC, ID";

if(strlen($gstrOrderBy) && strtolower(substr($gstrOrderBy,0,8))!="order by")

$gstrOrderBy="order by ".$gstrOrderBy;
// alias for 'SQLQuery' object

$gSettings = new ProjectSettings("Book_Display");

$gQuery = $gSettings->getSQLQuery();

$eventObj = &$tableEvents["BookDisplay"];
$reportCaseSensitiveGroupFields = false;
$gstrSQL = $gQuery->gSQLWhere(""); [b] // line 18 is here ??????[/b]_
In my Book_Display table - I have the two fields setup as default $_GET["fldcategory"] and the other field $_GET["fldavail"] and edit as text.
Any help would be greatly appreciated.