fix: Check mysqli connections with DO 1 instead of the deprecated ping().

system/core/CodeIgniter.php

@@ -56,7 +56,7 @@
  * @var	string
  *
  */
-	const CI_VERSION = '3.4.8';
+	const CI_VERSION = '3.4.9';
 
 /*
  * ------------------------------------------------------

system/database/drivers/mysqli/mysqli_driver.php

@@ -248,7 +248,7 @@ public function db_connect($persistent = FALSE)
 	 */
 	public function reconnect()
 	{
-		if ($this->conn_id !== FALSE && $this->conn_id->ping() === FALSE)
+		if ($this->conn_id !== FALSE && $this->conn_id->query('DO 1') === FALSE)
 		{
 			$this->conn_id = FALSE;
 		}

tests/codeigniter/database/Mysqli_reconnect_test.php

@@ -0,0 +1,44 @@
+<?php
+
+class Mysqli_reconnect_test extends CI_TestCase {
+
+	public function test_reconnect_detects_dropped_connection()
+	{
+		if (DB_DRIVER !== 'mysqli')
+		{
+			return $this->markTestSkipped('Requires the mysqli driver.');
+		}
+
+		$db = Mock_Database_Schema_Skeleton::init(DB_DRIVER);
+		$db->initialize();
+
+		$deprecations = array();
+		set_error_handler(function ($severity, $message) use (&$deprecations) {
+			$severity === E_DEPRECATED && $deprecations[] = $message;
+			return TRUE;
+		});
+
+		$db->reconnect();
+		$alive_after_live_check = ($db->conn_id !== FALSE);
+
+		$config = Mock_Database_DB::config(DB_DRIVER);
+		$config = $config[DB_DRIVER];
+		$admin = new mysqli($config['hostname'], $config['username'], $config['password'], $config['database']);
+		$admin->query('KILL '.$db->conn_id->thread_id);
+		$admin->close();
+		usleep(200000);
+
+		$db->reconnect();
+		$dropped_after_dead_check = ($db->conn_id === FALSE);
+
+		$query = $db->query('SELECT 1 AS one');
+
+		restore_error_handler();
+
+		$this->assertSame(array(), $deprecations);
+		$this->assertTrue($alive_after_live_check);
+		$this->assertTrue($dropped_after_dead_check);
+		$this->assertEquals(1, $query->row()->one);
+	}
+
+}