(PHP 4 >= 4.0.6, PHP 5)
openssl_x509_parse — Parse an X509 certificate and return the information as an array
   openssl_x509_parse() returns information about the
   supplied x509cert, including fields such as subject
   name, issuer name, purposes, valid from and valid to dates etc.
  
x509cert
shortnames
       shortnames controls how the data is indexed in the
       array - if shortnames is TRUE (the default) then
       fields will be indexed with the short name form, otherwise, the long name
       form will be used - e.g.: CN is the shortname form of commonName.
      
The structure of the returned data is (deliberately) not yet documented, as it is still subject to change.