While not specified in the description, this function, just like mcrypt_enc_get_key_size(), returns the cipher's largest key size in BYTES.
(PHP 4, PHP 5, PHP 7)
mcrypt_get_key_size — Gets the key size of the specified cipher
This function has been DEPRECATED as of PHP 7.1.0. Relying on this function is highly discouraged.
The first prototype is when linked against libmcrypt 2.2.x, the second when linked against libmcrypt 2.4.x or 2.5.x.
mcrypt_get_key_size() is used to get the size
of a key of the specified
combination with an encryption mode).
One of the
MCRYPT_ciphername constants, or the name of the algorithm as string.
One of the
MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".
Returns the maximum supported key size of the algorithm in bytes
FALSE on failure.
Example #1 mcrypt_get_key_size() Example
echo mcrypt_get_key_size('tripledes', 'ecb');
The example above shows how to use this function when linked against libmcrypt 2.4.x or 2.5.x.
The above example will output: