php: Move server code into new phpx package

internal/phpx/errors.go

@@ -0,0 +1,35 @@
+package phpx
+
+import "fmt"
+
+// Common PHP Errors
+const (
+	errInit    = "Server initialization failed"
+	errClosed  = "Server closed"
+	errReceive = "Failed to decode response"
+)
+
+// PHPError represents an error during PHPServer logic
+type ServerError struct {
+	Message string
+	Err     error
+}
+
+// Unwrap returns the underlying error
+func (err ServerError) Unwrap() error {
+	return err.Err
+}
+
+func (err ServerError) Error() string {
+	if err.Err == nil {
+		return fmt.Sprintf("PHPServer: %s", err.Message)
+	}
+	return fmt.Sprintf("PHPServer: %s: %s", err.Message, err.Err)
+}
+
+// Throwable represents an error during php code
+type Throwable string
+
+func (throwable Throwable) Error() string {
+	return string(throwable)
+}