Are you trying to do the search from a single text field ?
lets call your single search text field 'searchtext'
try this
//comparison list additions
$WADbSearch1->addComparisonFromEdit("PgTitle","searchtext","AND" ,"Includes",0);
$WADbSearch1->addComparisonFromEdit("PgDesc","searchtext","AND"," Includes",0);
$WADbSearch1->addComparisonFromEdit("PgDetails","searchtext"," AND","Includes",0);