diff --git a/lib/Cake/Model/Datasource/Database/Mysql.php b/lib/Cake/Model/Datasource/Database/Mysql.php
index 682c742f1..fb8a3455e 100644
--- a/lib/Cake/Model/Datasource/Database/Mysql.php
+++ b/lib/Cake/Model/Datasource/Database/Mysql.php
@@ -333,7 +333,7 @@ class Mysql extends DboSource {
  * Returns an array of the fields in given table name.
  *
  * @param Model|string $model Name of database table to inspect or model instance
- * @return array Fields in table. Keys are name and type
+ * @return array|bool Fields in table. Keys are name and type. Returns false if result is empty.
  * @throws CakeException
  */
 	public function describe($model) {
@@ -344,7 +344,7 @@ class Mysql extends DboSource {
 		}
 		$table = $this->fullTableName($model);
 
-		$fields = false;
+		$fields = array();
 		$cols = $this->_execute('SHOW FULL COLUMNS FROM ' . $table);
 		if (!$cols) {
 			throw new CakeException(__d('cake_dev', 'Could not describe table for %s', $table));
@@ -361,7 +361,8 @@ class Mysql extends DboSource {
 				$fields[$column->Field]['unsigned'] = $this->_unsigned($column->Type);
 			}
 			if (in_array($fields[$column->Field]['type'], array('timestamp', 'datetime')) &&
-				in_array(strtoupper($column->Default), array('CURRENT_TIMESTAMP', 'CURRENT_TIMESTAMP()'))
+				//Falling back to default empty string due to PHP8.1 deprecation notice.
+				in_array(strtoupper($column->Default ?? ""), array('CURRENT_TIMESTAMP', 'CURRENT_TIMESTAMP()'))
 			) {
 				$fields[$column->Field]['default'] = null;
 			}
@@ -382,6 +383,12 @@ class Mysql extends DboSource {
 		}
 		$this->_cacheDescription($key, $fields);
 		$cols->closeCursor();
+
+		//Fields must be an array for compatibility with PHP8.1 (deprecation notice) but also let's keep backwards compatibility for method.
+		if (count($fields) === 0) {
+			return false;
+		}
+
 		return $fields;
 	}
 
diff --git a/lib/Cake/Model/Datasource/DboSource.php b/lib/Cake/Model/Datasource/DboSource.php
index ebfab0a97..342ff9d17 100644
--- a/lib/Cake/Model/Datasource/DboSource.php
+++ b/lib/Cake/Model/Datasource/DboSource.php
@@ -2070,7 +2070,8 @@ class DboSource extends DataSource {
  * @return string
  */
 	public function renderJoinStatement($data) {
-		if (strtoupper($data['type']) === 'CROSS' || empty($data['conditions'])) {
+		//Fixed deprecation notice in PHP8.1 - fallback to empty string
+		if (strtoupper($data['type'] ?? "") === 'CROSS' || empty($data['conditions'])) {
 			return "{$data['type']} JOIN {$data['table']} {$data['alias']}";
 		}
 		return trim("{$data['type']} JOIN {$data['table']} {$data['alias']} ON ({$data['conditions']})");
diff --git a/lib/Cake/Routing/Route/CakeRoute.php b/lib/Cake/Routing/Route/CakeRoute.php
index 85dbb59c9..8149ce39a 100644
--- a/lib/Cake/Routing/Route/CakeRoute.php
+++ b/lib/Cake/Routing/Route/CakeRoute.php
@@ -470,7 +470,8 @@ class CakeRoute {
 		//check patterns for routed params
 		if (!empty($this->options)) {
 			foreach ($this->options as $key => $pattern) {
-				if (array_key_exists($key, $url) && !preg_match('#^' . $pattern . '$#', $url[$key])) {
+				//Fixing deprecation notice about null $subject in PHP8.1.
+				if (array_key_exists($key, $url) && !preg_match('#^' . $pattern . '$#', $url[$key] ?? "")) {
 					return false;
 				}
 			}