Add PHP's php-language-server to built-in guessed servers

Closes #1. The problem in that issue is that php-language-server has a
bug when it's not passed it the deprecated ":rootPath" field. The bug
doesn't happen if the ":processId" field is also absent. Eglot was
triggering the bug, because it didn't pass ":rootPath", but there's
nothing wrong in doing so.

* README.md: Add php-language-server to the built-in list.

* eglot.el (eglot-server-programs): Add php-language-server.
(eglot--connect): Also pass (deprecated) rootPath.

README.md

@@ -15,12 +15,13 @@ M-x eglot
 *That's it*. If you're lucky, this guesses the LSP executable to start
 for the language of your choice. Otherwise, it prompts you to enter one:
 
-`M-x eglot` currently guesses and works out-of-the-box with:
+`M-x eglot` can guess and work out-of-the-box with these servers:
 
 * Javascript's [javascript-typescript-stdio][javascript-typescript-langserver]
 * Rust's [rls][rls]
 * Python's [pyls][pyls]
 * Bash's [bash-language-server][bash-language-server]
+* PHP's [php-language-server][php-language-server]
 
 I'll add to this list as I test more servers. In the meantime you can
 customize `eglot-server-programs`:
@@ -193,6 +194,7 @@ Under the hood:
 [emacs-lsp]: https://github.com/emacs-lsp/lsp-mode
 [emacs-lsp-plugins]: https://github.com/emacs-lsp
 [bash-language-server]: https://github.com/mads-hartmann/bash-language-server
+[php-language-server]: https://github.com/felixfbecker/php-language-server
 [company-mode]: https://github.com/company-mode/company-mode
 
 

eglot.el

@@ -71,7 +71,9 @@
 (defvar eglot-server-programs '((rust-mode . ("rls"))
                                 (python-mode . ("pyls"))
                                 (js-mode . ("javascript-typescript-stdio"))
-                                (sh-mode . ("bash-language-server" "start")))
+                                (sh-mode . ("bash-language-server" "start"))
+                                (php-mode . ("php" "vendor/felixfbecker/\
+language-server/bin/php-language-server.php")))
   "Alist mapping major modes to server executables.")
 
 (defface eglot-mode-line
@@ -276,6 +278,7 @@ INTERACTIVE is t if inside interactive call."
                                                     'network)
                                           (emacs-pid))
                              :capabilities(eglot--client-capabilities)
+                             :rootPath  (car (project-roots project))
                              :rootUri  (eglot--path-to-uri
                                         (car (project-roots project)))
                              :initializationOptions  []))