Option 1

After you change PATH with the GUI, close and re-open the console window.

This works because only programs started after the change will see the new PATH.

Option 2

This option only affects your current shell session, not the whole system. Execute this command in the command window you have open:

set PATH=%PATH%;C:\your\path\here\

This command appends C:\your\path\here\ to the current PATH. If your path includes spaces, you do NOT need to include quote marks.

Breaking it down:

• set – A command that changes cmd's environment variables only for the current cmd session; other programs and the system are unaffected.
• PATH= – Signifies that PATH is the environment variable to be temporarily changed.
• %PATH%;C:\your\path\here\ – The %PATH% part expands to the current value of PATH, and ;C:\your\path\here\ is then concatenated to it. This becomes the new PATH.

WARNING: This solution may be destructive to your PATH, and the stability of your system. As a side effect, it will merge your user and system PATH, and truncate PATH to 1024 characters. The effect of this command is irreversible. Make a backup of PATH first. See the comments for more information.

Don't blindly copy-and-paste this. Use with caution.

You can permanently add a path to PATH with the setx command:

setx /M path "%path%;C:\your\path\here\"

Remove the /M flag if you want to set the user PATH instead of the system PATH.

Notes:

• The setx command is only available in Windows 7 and later.

• You should run this command from an elevated command prompt.

• If you only want to change it for the current session, use set.

You don't need any set or setx command. Simply open the terminal and type:

PATH

This shows the current value of PATH variable. Now you want to add directory to it? Simply type:

PATH %PATH%;C:\xampp\php

If for any reason you want to clear the PATH variable (no paths at all or delete all paths in it), type:

PATH ;

Update

Like Danial Wilson noted in comment below, it sets the path only in the current session. To set the path permanently, use setx but be aware, although that sets the path permanently, but not in the current session, so you have to start a new command line to see the changes. More information is here.

To check if an environmental variable exist or see its value, use the ECHO command:

echo %YOUR_ENV_VARIABLE%

I would use PowerShell instead!

To add a directory to PATH using PowerShell, do the following:

$PATH = [Environment]::GetEnvironmentVariable("PATH")
$xampp_path = "C:\xampp\php"
[Environment]::SetEnvironmentVariable("PATH", "$PATH;$xampp_path")

To set the variable for all users, machine-wide, the last line should be like:

[Environment]::SetEnvironmentVariable("PATH", "$PATH;$xampp_path", "Machine")

In a PowerShell script, you might want to check for the presence of your C:\xampp\php before adding to PATH (in case it has been previously added). You can wrap it in an if conditional.

So putting it all together:

$PATH = [Environment]::GetEnvironmentVariable("PATH", "Machine")
$xampp_path = "C:\xampp\php"
if( $PATH -notlike "*"+$xampp_path+"*" ){
    [Environment]::SetEnvironmentVariable("PATH", "$PATH;$xampp_path", "Machine")
}

Better still, one could create a generic function. Just supply the directory you wish to add:

function AddTo-Path{
param(
    [string]$Dir
)

    if( !(Test-Path $Dir) ){
        Write-warning "Supplied directory was not found!"
        return
    }
    $PATH = [Environment]::GetEnvironmentVariable("PATH", "Machine")
    if( $PATH -notlike "*"+$Dir+"*" ){
        [Environment]::SetEnvironmentVariable("PATH", "$PATH;$Dir", "Machine")
    }
}

You could make things better by doing some polishing. For example, using Test-Path to confirm that your directory actually exists.

Safer SETX

Nod to all the comments on the @Nafscript's initial SETX answer.

• SETX by default will update your user path.
• SETX ... /M will update your system path.
• %PATH% contains the system path with the user path appended

Warnings

1. Backup your PATH - SETX will truncate your junk longer than 1024 characters
2. Don't call SETX %PATH%;xxx - adds the system path into the user path
3. Don't call SETX %PATH%;xxx /M - adds the user path into the system path
4. Excessive batch file use can cause blindness¹

The ss64 SETX page has some very good examples. Importantly it points to where the registry keys are for SETX vs SETX /M

User Variables:

HKCU\Environment

System Variables:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environment