system/Session/Handlers/MemcachedHandler.php
public function read($sessionID): string
	{
		if (isset($this->memcached) && $this->lockSession($sessionID))
		{
			// Needed by write() to detect session_regenerate_id() calls
			$this->sessionID = $sessionID;

			$session_data      = (string) $this->memcached->get($this->keyPrefix . $sessionID);
			$this->fingerprint = md5($session_data);

			return $session_data;
		}

		return '';
	}
public function read($sessionID): string
	{
		if (isset($this->memcached) && $this->lockSession($sessionID))
		{
			// Needed by write() to detect session_regenerate_id() calls
			$this->sessionID = $sessionID;

			$session_data      = (string) $this->memcached->get($this->keyPrefix . $sessionID);
			$this->fingerprint = md5($session_data);

			return $session_data;
		}

		return '';
	}
Read

Reads session data and acquires a lock

@param string $sessionID Session ID

@return string    Serialized session data