Programming-questions about how PHP, such as curl and file_get_contents, can obtain webpage content Functions

If the URL is directly input in the browser, the content is correctly displayed, but an empty string is returned when the content is obtained by a function or component such as CURL or filegetcontents. This problem occurs when I used PHP to capture Baidu dictionary content. This also happens when I capture 12306 of data a few days ago. Please... if the URL is directly entered in the browser, the content is correctly displayed, but the CURL or file GetWhen a function or component such as contents obtains the content, an empty string is returned. This problem occurs when I used PHP to capture the content of Baidu dictionary. This also happened when I captured 12306 of the data a few days ago. How did they identify it? Is there any solution? Thank you!

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If the URL is directly entered in the browser, the content is correctly displayed, but the CURL or fileGetWhen a function or component such as contents obtains the content, an empty string is returned. This problem occurs when I used PHP to capture the content of Baidu dictionary. This also happened when I captured 12306 of the data a few days ago. How did they identify it? Is there any solution? Thank you!

1. Set user_agent to the browser. 2. Set referrer correctly. 3. Add cookie4. other additional items.