Send password to PHP text file on internet without 'GET' request

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C#

PHP

Hello guys. I want to send passwords from my Visual Studio C# application to a php text file hosted on the internet. Therefore, I am using this code:

public void SendPassword(string password)
       {

           string info = computerName + "-" + userName + " " + password;
           var fullUrl = targetURL + info;
           var conent = new System.Net.WebClient().DownloadString(fullUrl);

Unfortunately, my friends are saying that this is not a safe method because the password is being sent to the server with a GET request unencrypted. Any suggestions on how I can do this safely? Thanks :)

What I have tried:

I have tried googling it, but didn't find what I was looking for.