Warning: Cannot modify header information - headers already sent by (output started at file_path:line)

"Warning: Cannot modify header information - headers already sent by (output started at file_path:line)"

• 原因：嘗試修改HTTP頭資訊，但已有內容輸出。
• 解決方法：確保在任何輸出前設定HTTP頭資訊，檢查是否有空白字元或註釋提前輸出。