Regular Expression to get the whole Comma Separated String in Array Key

Hi All, Need help in resolving the below problem- I would like to get the whole comma separated string into an array value- 1. $postText = "chapters 5, 6, 7, 8"; OR 2. $postText = "chapters 5, 6; OR 3. $postText = "chapters 5, 6, 7"; What i have done so far is- preg_match('/chapter[s]*[ ]*(\d+, \d+, \d+)/i', $postText, $matches); The above will exactly match the third value $postText = "chapters 5, 6, 7"; By Above $matches will contain a value of : $matches[1] = '5, 6, 7'; Now i need a SINGLE regular expression which can match first, second variable above or any number of comma separated string and IMPORTANTLY provide me that whole comma separated sting value (as above) in single array key element like below- $matches[1] = '5, 6, 7'; OR $matches[1] = '5, 6'; OR $matches[1] = '5, 6, 7, 8, 9'; Also I have to use regular expression only as the flow of the code does not permit to use any other method to get comma separated string from the master/base string. Thanks, Gaurav Kumar