Database wrapper for Codeigniter 3

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

// This class serves as our own wrapper for CodeIgniter's built-in database class
class Dw_database {

	private $CI;
	private $requests;
	private $master_conn;
	private $slave_conn;
	public $transaction_status;

	// Read rows from the database
	public function read($query = '')
	{
	    $time = microtime(true);

	    $this->requests++;

		$response = $this->CI->db->query($query);

		$time = microtime(true) - $time;
		$class_name = strtolower($this->CI->router->class);

		if ($class_name != 'cron' AND $time > 1)
		{
		    file_put_contents(STATIC_PATH . '/httpdocs/application/logs/database.php', date('Y-m-d H:i:s') . " => $time => " . uri_string() . " $query\n", FILE_APPEND);
		}

		return $response;
	}
	
	// Read rows from the slave
	public function read_slave($query = '')
	{	    
	    $time = microtime(true);	    
	    
	    if ($this->slave_conn === null)
	    {
	        // Load CodeIgniter's built-in database class
	        $this->slave_conn = $this->CI->load->database('slave', true);	        
	    }	    
	    
	    $this->requests++;
	    
	    $response = $this->slave_conn->query($query);
	    
	    $time = microtime(true) - $time;
	    
	    if ($time > 30)
	    {
	        file_put_contents(STATIC_PATH . '/httpdocs/application/logs/database_slave.php', date('Y-m-d H:i:s') . " => $time => " . uri_string() . " $query\n", FILE_APPEND);
	    }
	    
	    return $response;
	}
	
	public function read_slave_unbuffered($query = '')
	{	    
	    if ($this->slave_conn === null)
	    {
	        // Load CodeIgniter's built-in database class
	        $this->slave_conn = $this->CI->load->database('slave', true);	        
	    }
	    
	    return $this->slave_conn->conn_id->query($query, MYSQLI_USE_RESULT);
	}
	
	public function read_unbuffered($query = '')
	{
	    return $this->CI->db->conn_id->query($query, MYSQLI_USE_RESULT);
	}

	// Write to the database
	public function write($query = '', $get_id = false)
	{
	    $time = microtime(true);

	    $this->requests++;
	    
	    $i = 0;
		
		// If the query failed ...
		while ($this->CI->db->query($query) === false)
		{
		    // file_put_contents('/home/daniweb/httpdocs/application/logs/db_lock.php', date('Y-m-d H:i:s') . " => " . uri_string() . " => " . json_encode($_POST) . " $query\n", FILE_APPEND);		    
		    
		    // Try again
		    		    
		    if (is_cli())
		    {
		        sleep(5);
		    }
		    else
		    {
		        usleep(10000);
		    }
		    
		    $i++;
		    		    
		    // Query failed many times
		    if ($i > 5)
		    {
		        // file_put_contents('/home/daniweb/httpdocs/application/logs/db_lock_fail.php', date('Y-m-d H:i:s') . " => " . uri_string() . " => " . json_encode($_POST) . " $query\n", FILE_APPEND);
		        
		        $this->transaction_status = false;
		        
		        return 0;
		    }
		}

		if ($get_id)
		{
			$response = $this->CI->db->insert_id();
		}
		else
		{
			$response = $this->CI->db->affected_rows();
		}
		
		$time = microtime(true) - $time;
		$class_name = strtolower($this->CI->router->class);

		/*
		if ($class_name != 'cron' AND $time > 1)
		{
	       file_put_contents('/home/daniweb/httpdocs/application/logs/database.php', date('Y-m-d H:i:s') . " => $time => " . uri_string() . " $query\n", FILE_APPEND);
		}
		*/

		return $response;
	}

	public function requests()
	{
	    return $this->requests;
	}

	// Escape a string and encase it in single quotes (for use in DB queries)
	public function escape($string = '')
	{
	    return $this->CI->db->escape($string);
	    // return $this->CI->db->escape(filter_var($string, FILTER_UNSAFE_RAW, array('flags' => FILTER_FLAG_STRIP_HIGH)));
	}

	// Constructor function
	public function __construct()
	{
	    $this->requests = 0;

		$this->CI =& get_instance();

		// Load CodeIgniter's built-in database class
		// $this->master_conn = $this->CI->load->database('master', true);

		// Load Cache
		$this->CI->load->driver('cache', array('adapter' => 'memcached'));

		// $this->CI->output->enable_profiler(TRUE);	
		
		if ($this->CI->input->server('REQUEST_METHOD') == 'POST')
		{
	       $this->CI->db->trans_begin();
	       
	       // Maintain our own transaction status
	       $this->transaction_status = true;
		}
	}

	public function __destruct()
	{	    
	    if ($this->CI->input->server('REQUEST_METHOD') == 'POST')
	    {
	        if ($this->transaction_status === false)
	        {
	            $this->CI->db->trans_rollback();
	        }
	        else
	        {
	            $this->CI->db->trans_commit();
	        }
	    }
	}
}