Change version of PHP in Valet+

switch-php() {
    valet stop
    brew unlink php@7.2 php@7.3 php@7.4
    brew link --force --overwrite php@$1
    brew services restart php@$1
    composer global update
    rm -f ~/.config/valet/valet.sock
    valet install
}

Alternative for the brew unlink line:

brew list --formula -1 | grep php | grep @ | xargs brew unlink

This will unlink all php versions you have installed, without manually having to list them all.