PHP/Utility Function/mcrypt enc get iv size

Using Mcrypt generic

 
<?php
    $plaintext = "this is a test";
    $password = "enigma";
    $cipher = mcrypt_module_open("blowfish", "", "ecb", "");
    $iv_size = mcrypt_enc_get_iv_size($cipher);
    srand();
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    mcrypt_generic_init($cipher, $password, $iv);
    $ciphertext = mcrypt_generic($cipher, $plaintext);
    mcrypt_generic_deinit($cipher);
    mcrypt_module_close($cipher);
    file_put_contents("secret_message.txt", $iv . $ciphertext);
?>