How to transfer PHP native PDF to base64?

problem description

padf  base64

the environmental background of the problems and what methods you have tried

related codes

/ / Please paste the code text below (do not replace the code with pictures)

 try{
            $tmp_file="./pic/8.14/".$row["id"].".pdf";
            if(file_exists($tmp_file)){
                
                
                $file=$this->imgToBase64($tmp_file);
                $fileName=$row["id"].".pdf";
                
                echo("<iframe src="". $fileContent."style="width:1024px;height:800px;"></iframe>"."<br> ------------<br>");

            }

what result do you expect? What is the error message actually seen?

Php
Apr.11,2021
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