diff --git a/phpQuery/phpQuery.php b/phpQuery/phpQuery.php
index 118c94b..0788f7a 100644
--- a/phpQuery/phpQuery.php
+++ b/phpQuery/phpQuery.php
@@ -647,7 +647,7 @@ public static function DOMNodeListToArray($DOMNodeList) {
 	 * @todo still used ?
 	 */
 	public static function isMarkup($input) {
-		return ! is_array($input) && substr(trim($input), 0, 1) == '<';
+		return ! is_array($input) && substr(trim($input ?? ''), 0, 1) == '<';
 	}
 	public static function debug($text) {
 		if (self::$debug)
diff --git a/phpQuery/phpQuery/DOMDocumentWrapper.php b/phpQuery/phpQuery/DOMDocumentWrapper.php
index aae5ee0..7ddd485 100644
--- a/phpQuery/phpQuery/DOMDocumentWrapper.php
+++ b/phpQuery/phpQuery/DOMDocumentWrapper.php
@@ -44,15 +44,17 @@ class DOMDocumentWrapper {
 	public $isXHTML = false;
 	public $isHTML = false;
 	public $charset;
-	public function __construct($markup = null, $contentType = null, $newDocumentID = null) {
+	public function __construct($markup = null, $contentType = '', $newDocumentID = null) {
 		if (isset($markup))
 			$this->load($markup, $contentType, $newDocumentID);
 		$this->id = $newDocumentID
 			? $newDocumentID
 			: md5(microtime());
 	}
-	public function load($markup, $contentType = null, $newDocumentID = null) {
+	public function load($markup, $contentType = '', $newDocumentID = null) {
 //		phpQuery::$documents[$id] = $this;
+        if ($contentType === null)
+            $contentType = '';
 		$this->contentType = strtolower($contentType);
 		if ($markup instanceof DOMDOCUMENT) {
 			$this->document = $markup;
@@ -131,7 +133,7 @@ protected function documentCreate($charset, $version = '1.0') {
 		$this->document->formatOutput = true;
 		$this->document->preserveWhiteSpace = true;
 	}
-	protected function loadMarkupHTML($markup, $requestedCharset = null) {
+	protected function loadMarkupHTML($markup, $requestedCharset = '') {
 		if (phpQuery::$debug)
 			phpQuery::debug('Full markup load (HTML): '.substr($markup, 0, 250));
 		$this->loadMarkupReset();
@@ -153,11 +155,11 @@ protected function loadMarkupHTML($markup, $requestedCharset = null) {
 		// @see http://www.w3.org/International/O-HTTP-charset
 		if (! $documentCharset) {
 			$documentCharset = 'ISO-8859-1';
-			$addDocumentCharset = true;	
+			$addDocumentCharset = true;
 		}
 		// Should be careful here, still need 'magic encoding detection' since lots of pages have other 'default encoding'
 		// Worse, some pages can have mixed encodings... we'll try not to worry about that
-		$requestedCharset = strtoupper($requestedCharset);
+		$requestedCharset = $requestedCharset ? strtoupper($requestedCharset) : '';
 		$documentCharset = strtoupper($documentCharset);
 		phpQuery::debug("DOC: $documentCharset REQ: $requestedCharset");
 		if ($requestedCharset && $documentCharset && $requestedCharset !== $documentCharset) {
@@ -441,7 +443,7 @@ public function import($source, $sourceCharset = null) {
 //					if ($fake === false)
 //						throw new Exception("Error loading documentFragment markup");
 //					else
-//						$return = array_merge($return, 
+//						$return = array_merge($return,
 //							$this->import($fake->root->childNodes)
 //						);
 //				} else {
@@ -510,7 +512,7 @@ protected function documentFragmentCreate($source, $charset = null) {
 	 * @param $markup
 	 * @return $document
 	 */
-	private function documentFragmentLoadMarkup($fragment, $charset, $markup = null) {
+	private function documentFragmentLoadMarkup($fragment, $charset, $markup = '') {
 		// TODO error handling
 		// TODO copy doctype
 		// tempolary turn off
diff --git a/phpQuery/phpQuery/phpQueryObject.php b/phpQuery/phpQuery/phpQueryObject.php
index be31e65..f097eac 100644
--- a/phpQuery/phpQuery/phpQueryObject.php
+++ b/phpQuery/phpQuery/phpQueryObject.php
@@ -313,7 +313,7 @@ protected function parseSelector($query) {
 		// TODO include this inside parsing ?
 		$query = trim(
 			preg_replace('@\s+@', ' ',
-				preg_replace('@\s*(>|\\+|~)\s*@', '\\1', $query)
+				preg_replace('@\s*(>|\\+|~)\s*@', '\\1', $query ?? '')
 			)
 		);
 		$queries = array(array());
@@ -1672,9 +1672,11 @@ public function size() {
 	 * @return phpQueryObject|QueryTemplatesSource|QueryTemplatesParse|QueryTemplatesSourceQuery
 	 * @deprecated Use length as attribute
 	 */
+    #[\ReturnTypeWillChange]
 	public function length() {
 		return $this->size();
 	}
+    #[\ReturnTypeWillChange]
 	public function count() {
 		return $this->size();
 	}
@@ -2989,6 +2991,7 @@ public function removeData($key) {
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function rewind(){
 		$this->debug('iterating foreach');
 //		phpQuery::selectDocument($this->getDocumentID());
@@ -3004,12 +3007,14 @@ public function rewind(){
 	/**
    * @access private
 	 */
-	public function current(){
+    #[\ReturnTypeWillChange]
+	public function current() {
 		return $this->elementsInterator[ $this->current ];
 	}
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function key(){
 		return $this->current;
 	}
@@ -3024,7 +3029,8 @@ public function key(){
 	 * @see phpQueryObject::_next()
 	 * @return phpQueryObject|QueryTemplatesSource|QueryTemplatesParse|QueryTemplatesSourceQuery
 	 */
-	public function next($cssSelector = null){
+    #[\ReturnTypeWillChange]
+	public function next($cssSelector = null) {
 //		if ($cssSelector || $this->valid)
 //			return $this->_next($cssSelector);
 		$this->valid = isset( $this->elementsInterator[ $this->current+1 ] )
@@ -3041,6 +3047,7 @@ public function next($cssSelector = null){
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function valid(){
 		return $this->valid;
 	}
@@ -3049,18 +3056,21 @@ public function valid(){
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function offsetExists($offset) {
 		return $this->find($offset)->size() > 0;
 	}
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function offsetGet($offset) {
 		return $this->find($offset);
 	}
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function offsetSet($offset, $value) {
 //		$this->find($offset)->replaceWith($value);
 		$this->find($offset)->html($value);
@@ -3068,6 +3078,7 @@ public function offsetSet($offset, $value) {
 	/**
    * @access private
 	 */
+    #[\ReturnTypeWillChange]
 	public function offsetUnset($offset) {
 		// empty
 		throw new Exception("Can't do unset, use array interface only for calling queries and replacing HTML.");