Swap static variable for shared reference to object

include/tcpdf_page_cache_reference_counts.php

@@ -0,0 +1,75 @@
+<?php
+//============================================================+
+// File name   : tcpdf_page_cache_reference_counts.php
+// Version     : 1.0.000
+// Begin       : 2023-08-04
+// Last Update : 2023-08-04
+// License     : GNU-LGPL v3 (http://www.gnu.org/copyleft/lesser.html)
+// -------------------------------------------------------------------
+// Copyright (C) 2002-2013  Nicola Asuni - Tecnick.com LTD
+//
+// This file is part of TCPDF software library.
+//
+// TCPDF is free software: you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// TCPDF is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with TCPDF.  If not, see <http://www.gnu.org/licenses/>.
+//
+// See LICENSE.TXT file for more information.
+// -------------------------------------------------------------------
+//
+// Description : Class to keep track of page cache references
+//
+//============================================================+
+
+/**
+ * @file
+ * PHP page cache reference counts class for TCPDF
+ * @package com.tecnick.tcpdf
+ */
+
+/**
+ * @class TCPDF_PAGE_CACHE_REFERENCE_COUNTS
+ * PHP page cache reference counts class for TCPDF
+ * @package com.tecnick.tcpdf
+ * @version 1.0.000
+ */
+class TCPDF_PAGE_CACHE_REFERENCE_COUNTS
+{
+	/** @var int Number of references */
+	private $numReferences = 0;
+
+	/**
+	 * Increment reference count
+	 */
+	public function incrementReferenceCount()
+	{
+		$this->numReferences++;
+	}
+
+	/**
+	 * Decrement reference count
+	 */
+	public function decrementReferenceCount()
+	{
+		$this->numReferences--;
+	}
+
+	/**
+	 * Get reference count
+	 *
+	 * @return int Reference count
+	 */
+	public function getReferenceCount()
+	{
+		return $this->numReferences;
+	}
+}

tcpdf.php

@@ -119,6 +119,8 @@
 require_once(dirname(__FILE__).'/include/tcpdf_images.php');
 // TCPDF static methods and data
 require_once(dirname(__FILE__).'/include/tcpdf_static.php');
+// TCPDF page cache reference counts
+require_once(dirname(__FILE__).'/include/tcpdf_page_cache_reference_counts.php');
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
@@ -195,6 +197,13 @@ class TCPDF {
 	 */
 	protected $pageCacheIndex = array();
 
+	/**
+	 * Page cache reference counts
+	 * @protected
+	 * @var TCPDF_PAGE_CACHE_REFERENCE_COUNTS|null
+	 */
+	protected $pageCacheRefCnts = null;
+
 	/**
 	 * Current document state.
 	 * @protected
@@ -7912,9 +7921,6 @@ public function _destroy($destroyall=false, $preserve_objcopy=false) {
 		}
 	}
 
-	/** Page cache reference counts */
-	protected static $pageCacheRefCnts = array();
-
 	/**
 	 * Update page cache file
 	 *
@@ -7927,7 +7933,9 @@ public function usePageCacheFile($memSizeInBytes)
 		if ($this->pageCacheFile === false) {
 			$this->pageCacheFile = null;
 		} else {
-			self::$pageCacheRefCnts[(int)$this->pageCacheFile] = 1;
+			if ($this->pageCacheRefCnts == null)
+				$this->pageCacheRefCnts = new TCPDF_PAGE_CACHE_REFERENCE_COUNTS();
+			$this->pageCacheRefCnts->incrementReferenceCount();
 		}
 	}
 
@@ -7938,8 +7946,8 @@ private function _closePageCacheFile()
 	{
 		if ($this->pageCacheFile !== null)
 		{
-			self::$pageCacheRefCnts[(int)$this->pageCacheFile]--;
-			if (self::$pageCacheRefCnts[(int)$this->pageCacheFile] == 0) {
+			$this->pageCacheRefCnts->decrementReferenceCount();
+			if ($this->pageCacheRefCnts->getReferenceCount() == 0) {
 				// This might be the end of the PHP script and the temporary file may be
 				// removed before this class, so check if it's still a valid resource.
 				if (is_resource($this->pageCacheFile)) {
@@ -7961,7 +7969,7 @@ public function __clone()
 		// Update ref count
 		if ($this->pageCacheFile !== null)
 		{
-			self::$pageCacheRefCnts[(int)$this->pageCacheFile]++;
+			$this->pageCacheRefCnts->incrementReferenceCount();
 			$this->roPageCacheFile = true;
 		}
 	}
@@ -21044,13 +21052,15 @@ protected function getPageBuffer($page) {
 					{
 						$origPageCacheFile = $this->pageCacheFile;
 						// Remove reference count to file and open a new page cache file
-						self::$pageCacheRefCnts[(int)$this->pageCacheFile]--;
+						$this->pageCacheRefCnts->decrementReferenceCount();
 						$this->pageCacheFile = fopen('php://temp', 'w+');
 						if ($this->pageCacheFile === false) {
 							$this->pageCacheFile = null;
+							$this->pageCacheRefCnts = null;
 						} else {
 							// Add reference to new page cache file
-							self::$pageCacheRefCnts[(int)$this->pageCacheFile] = 1;
+							$this->pageCacheRefCnts = new TCPDF_PAGE_CACHE_REFERENCE_COUNTS();
+							$this->pageCacheRefCnts->incrementReferenceCount();
 							// Copy data from old page cache file to new one
 							fseek($origPageCacheFile, 0, SEEK_SET);
 							while (($copyContent = fread($origPageCacheFile, 8192)) != false) {