How can one ensure the integrity of PDF files when storing and retrieving them from a database in PHP?

To ensure the integrity of PDF files when storing and retrieving them from a database in PHP, one can calculate the checksum of the PDF file before storing it in the database. When retrieving the file, calculate the checksum again and compare it with the stored checksum to verify the integrity of the file. 

// Calculate checksum of the PDF file before storing it in the database
$pdf_file = 'path/to/pdf/file.pdf';
$checksum = md5_file($pdf_file);

// Store the PDF file along with the checksum in the database

// Retrieve the PDF file from the database
// Calculate the checksum of the retrieved file
$retrieved_pdf_file = 'path/to/retrieved/pdf/file.pdf';
$retrieved_checksum = md5_file($retrieved_pdf_file);

// Compare the checksums to verify the integrity of the PDF file
if ($checksum === $retrieved_checksum) {
    echo 'PDF file is intact and has not been tampered with.';
} else {
    echo 'PDF file may have been altered or corrupted.';
}

Keywords

PDF integrity database storage retrieval

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