php: Move server code into new phpx package

internal/phpx/php.go

@@ -0,0 +1,18 @@
+// Package phpx provides functionalities for interacting with PHP code
+package phpx
+
+import "github.com/tkw1536/goprogram/stream"
+
+// Executor represents anything that can spawn
+type Executor interface {
+	// Spawn spawns a new (independent) process executing code.
+	// It should return only once the execution terminates.
+	Spawn(str stream.IOStream, code string) error
+}
+
+// SpawnFunc implements Executor
+type SpawnFunc func(str stream.IOStream, code string) error
+
+func (sf SpawnFunc) Spawn(str stream.IOStream, code string) error {
+	return sf(str, code)
+}