在PHP中保护SMTP密码

I'm going to use the phpmailer class in my WordPress-plugin to support the use of SMTP in my e-mail function. Is it safe to store the password in the PHP code? I don't feel 100% comfortable with leaving my login there. So my questions: Is it safe enough? How can I easily make it more secure; should I hash it in a database or something? I know MD5 isn't really that secure, but I guess it is better than putting the password in the source code?I'm going to use the phpmailer class in my Word