(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.
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.