(PHP 4 >= 4.0.6, PHP 5, PHP 7)
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.
  
x509certX509 certificate. See Key/Certificate parameters for a list of valid values.
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.