mcrypt_get_iv_size Returns the size of the IV belonging to a specific cipher/mode combination &warn.deprecated.function-7-1-0; &reftitle.description; intmcrypt_get_iv_size stringcipher stringmode Gets the size of the IV belonging to a specific cipher/mode combination. It is more useful to use the mcrypt_enc_get_iv_size function as this uses the resource returned by mcrypt_module_open. &reftitle.parameters; cipher &mcrypt.parameter.cipher; mode &mcrypt.parameter.mode; The IV is ignored in ECB mode as this mode does not require it. You will need to have the same IV (think: starting point) both at encryption and decryption stages, otherwise your encryption will fail. &reftitle.returnvalues; Returns the size of the Initialization Vector (IV) in bytes. On error the function returns &false;. If the IV is ignored in the specified cipher/mode combination zero is returned. &reftitle.examples; ]]> &reftitle.seealso; mcrypt_get_block_size mcrypt_enc_get_iv_size mcrypt_create_iv