Encrypt/decrypt PHP function
In all reality the safety of the Data can be affected by any part of the transportation process, So just seeing how you encrypt and decrypt the information doesn't really help us help you in determining the safety of the data.



Nothing to do with the Security of the Functions

what you should do is create one function that will accept a parameter of encrypt or decrypt most of the information that you are using in both functions is duplicated.

function encryptOrDecrypt($mprhase, $crypt) {
     $MASTERKEY = "KEY PHRASE!";
     $td = mcrypt_module_open('tripledes', '', 'ecb', '');
     $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
     mcrypt_generic_init($td, $MASTERKEY, $iv);
     if ($crypt == 'encrypt')
     {
         $return_value = base64_encode(mcrypt_generic($td, $mprhase));
     }
     else
     {
         $return_value = mdecrypt_generic($td, base64_decode($mprhase));
     }
     mcrypt_generic_deinit($td);
     mcrypt_module_close($td);
     return $return_value;
} 


obviously some of the variables have been changed to protect the innocent, (in other words you should change the variable $return_value to something more meaningful)

(another note: you might want to fiddle around with the input parameter that I added as well.) 



Additional Important Information

As Corbin Pointed out, this should be a class/object that has methods for encrypting and deciphering and the whole works that go along with a class/object, unfortunately I don't know PHP syntax well enough to write it out.

a Function can do this, but it is sloppy coding, and I should have said this from the get go, I apologize.

I will look into the syntax when I have time or you can Visit this Fun page Or you can use ol' reliable