use ENV variables instead of hardcoded values

docker/php/.htaccess

@@ -0,0 +1,16 @@
+
+# BEGIN WordPress
+RewriteEngine On
+RewriteBase /
+RewriteRule ^index\.php$ - [L]
+
+# add a trailing slash to /wp-admin
+RewriteRule ^wp-admin$ wp-admin/ [R=301,L]
+
+RewriteCond %{REQUEST_FILENAME} -f [OR]
+RewriteCond %{REQUEST_FILENAME} -d
+RewriteRule ^ - [L]
+RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
+RewriteRule ^(.*\.php)$ wp/$1 [L]
+RewriteRule . index.php [L]
+# END WordPress