indents(php): align with C indentation

Fixes https://github.com/nvim-treesitter/nvim-treesitter/issues/2357

tests/indent/php_spec.lua

@@ -0,0 +1,20 @@
+local Runner = require("tests.indent.common").Runner
+
+local run = Runner:new(it, "tests/indent/php", {
+  tabstop = 4,
+  shiftwidth = 4,
+  softtabstop = 0,
+  expandtab = true,
+})
+
+describe("indent PHP:", function()
+  describe("whole file:", function()
+    run:whole_file(".", {
+      expected_failures = {},
+    })
+  end)
+
+  describe("new line:", function()
+    run:new_line("example.php", { on_line = 11, text = "// new line starts 1 indentation to far", indent = 4 })
+  end)
+end)