Query whether a certain pdf file exists in the server

Dear masters, please provide a query to see if a certain pdf file exists in the server. If it exists, it will be opened. If it does not exist, the user will be prompted to re-enter.

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Dear masters, please provide a query to see if a certain pdf file exists in the server. If it exists, it will be opened. If it does not exist, the user will be prompted to re-enter.

Make a judgment first and then perform the corresponding operation.

<code>$fileName = "text.pdf";
if(file_exists($fileName)) {
    Header("Location: $fileName"); 
} else {
    echo  '<script> alert("文件不存在") </script>';
    //die(json_encode(array("code"=> 404, "message"=> "文件不存在")));
}</code>