## Signature Algorithms

`OPENSSL_ALGO_DSS1` (integer)
`OPENSSL_ALGO_SHA1` (integer)
  Used as default algorithm by openssl_sign() and openssl_verify().
`OPENSSL_ALGO_SHA224` (integer)
  Added in PHP 5.4.8.
`OPENSSL_ALGO_SHA256` (integer)
  Added in PHP 5.4.8.
`OPENSSL_ALGO_SHA384` (integer)
  Added in PHP 5.4.8.
`OPENSSL_ALGO_SHA512` (integer)
  Added in PHP 5.4.8.
`OPENSSL_ALGO_RMD160` (integer)
  Added in PHP 5.4.8.
`OPENSSL_ALGO_MD5` (integer)
`OPENSSL_ALGO_MD4` (integer)
`OPENSSL_ALGO_MD2` (integer)
  As of PHP 5.2.13 and PHP 5.3.2, this constant is only available if PHP is compiled with MD2 support. This requires passing in the -DHAVE_OPENSSL_MD2_H CFLAG when compiling PHP, and enable-md2 when compiling OpenSSL 1.0.0+.