Decryption function in PHP returning a value of 1 (What am I doing wrong?)

Question

This is the method

public function _PRZ_decrypt_data($_salt, $_input)
{   
    return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $_salt, $_input, MCRYPT_MODE_ECB, $this->_PRZ_get_iv()));
}

I am calling it as one of my parameters as follows

$this->_PRZ_decrypt_data($salt, base64_decode($code))

It seems to be returning a 1 when a properly endoded value is decoded via the function.