this question has answer here:                               delimiter must not alphanumeric or backslash , preg_match                                         5 answers                                          this question has been asked don't know how fix problem in situation. getting following php errror:      php message: php warning:  preg_match(): delimiter must not alphanumeric or backslash in... on line 227    line 227 following:   if (preg_match($match, $_server['http_user_agent']))   and function:   $oslist = array ( 'windows 3.11' => 'win16', 'windows 95' => '(windows 95)|(win95)|(windows_95)', 'windows 98' => '(windows 98)|(win98)', 'windows 2000' => '(windows nt 5.0)|(windows 2000)', 'windows xp' => '(windows nt 5.1)|(windows xp)', 'windows server 2003' => '(windows nt 5.2)', 'windows vista' => '(windows nt 6.0)', 'w...