Warning: include(PhpSerial.php): failed to open stream: No such file or directory in D:\php\php_serial\examples\sms.php on line 2

Warning: include(): Failed opening 'PhpSerial.php' for inclusion (include_path='D:\Portable\xammp\php\PEAR') in D:\php\php_serial\examples\sms.php on line 2

Fatal error: Uncaught Error: Class 'PhpSerial' not found in D:\php\php_serial\examples\sms.php:5 Stack trace: #0 {main} thrown in D:\php\php_serial\examples\sms.php on line 5