fix: use static instance instead of new construction

src/BookSearch/BookSearch.php

@@ -17,7 +17,13 @@ class BookSearch
     /** @var array parts of the filter query, parameter 'fq' */
     private $filterQueryParts = array();
 
-    public function __construct(string $hostname, int $port, string $login, string $password, string $core, $edismax = true)
+    /**
+     * Last created instance
+     * @var BookSearch|null
+     */
+    private static $lastInstance = null;
+
+    public function __construct(string $hostname, int $port, string $login, string $password, string $core, bool $edismax = true)
     {
         $path = 'solr/' . $core;
 
@@ -35,6 +41,14 @@ class BookSearch
         // most options like search fields, sorting, etc are already set
         // as default in the Solr config and thus should be set only on a
         // per request basis when needed
+        self::$lastInstance = $this;
+    }
+
+    public static function getLastInstance(): BookSearch {
+        if (self::$lastInstance === null) {
+            throw new \Exception('No instance was ever created, make sure to call new BookSearch(...) somewhere in your code.');
+        }
+        return self::$lastInstance;
     }
 
     public function setHandler($handler)
@@ -280,7 +294,7 @@ class BookSearch
             return $books;
         }
 
-        $bs = new static();
+        $bs = self::getLastInstance();
         $bs->addOrQuery($codes, $field);
 
         $results = $bs->getResults(0, $count);
@@ -288,7 +302,7 @@ class BookSearch
     }
 
     public static function getTerms($field) {
-        $s = new BookSearch();
+        $s = self::getLastInstance();
         $s->addFilterQuery(1, 'visible');
         $s->addFacetField($field);
         $s->setFacetLimits(2000, 2);
@@ -299,7 +313,7 @@ class BookSearch
 
 
     public static function getTermsRange($field) {
-        $s = new BookSearch();
+        $s = self::getLastInstance();
         $s->addFilterQuery(1, 'visible');
         $s->setFacetRangeField($field);
         $s->setFacetRange(0, 250 * 60, 30);