PHP Functions Used by OpenSSL

OpenSSL is a library for cryptographic functions used by php. It offers functionality for signing (encrypting) and verifying signatures as well as for sealing (encrypting) data.

In PHP 8.0 and later, the is_resource function no longer returns true for all return values from OpenSSL extension functions. Existing code that uses is_resource to check for the presence of an OpenSSL resource should be updated to use the class name if it is known, or the function call if not known.

The openssl_pkey_new function returns an instance of the OpenSSLAsymmetricKey class instead of the OpenSSL key resource it did in PHP versions prior to 8.0. All functions that accepted the key resource will accept the class object as well.

The openssl_pkcs7_encrypt() and openssl_pkcs7_sign() functions encrypt data by using an RC2 40-bit cipher so that it can only be read by the intended recipients specified in the recipcerts argument.

The openssl_pkcs7_verify() function verifies the S/MIME message contained in the given file. Normally the input is converted to "canonical" format (which effectively uses CR and LF as end of line) as required by the S/MIME specification. This option makes no translation, and thus is useful when working with binary data that may not be in the MIME format. When verifying a signed message, certificates included with the signature are normally searched for the signers certificate. This option disables the chain verification of these certificates, and only the certificates specified in the extracerts argument to the function are verified.