When generating PDFs with TCPDF, handling large datasets can lead to errors such as:

Fatal error: Maximum execution time of 30 seconds exceeded
Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 72 bytes)

This issue occurs when TCPDF tries to handle too much data in memory. Increasing the memory limit alone is not always effective. Here's a comprehensive guide to resolve this problem.

Root Cause

TCPDF processes data in memory. When dealing with large datasets, the memory limit and execution time may be exceeded.

Step-by-step Solution

1. Optimize Data Handling

• Load data in chunks to avoid memory overload.

• Limit the number of records processed at a time.

2. Use Output Buffering

Redirect output to a file to reduce memory usage:

ob_start();
$pdf->Output('largefile.pdf', 'S'); // S means return as a string
$content = ob_get_clean();
file_put_contents('largefile.pdf', $content);

3. Clear Unused Variables

Explicitly unset large arrays or objects to free up memory:

unset($data);
gc_collect_cycles(); // Force garbage collection

4. Increase Memory Limit and Execution Time

In your script:

ini_set('memory_limit', '512M');
ini_set('max_execution_time', 300); // 5 minutes

5. Generate PDF in Smaller Batches

Generate the PDF in smaller sections and merge them later using tools like PDFtk or FPDI.

Example:

$pdf = new TCPDF();
$pdf->AddPage();

for ($i = 1; $i <= 1000; $i++) {
    $pdf->Cell(0, 10, "Record $i", 0, 1);
    if ($i % 100 == 0) {
        $pdf->Output('partial_' . $i . '.pdf', 'F');
        $pdf->AddPage(); // Add a new page for the next batch
    }
}

$pdf->Output('final.pdf', 'F');

6. Reduce Image Size and Quality

If embedding images, lower the resolution and compression:

$pdf->setImageScale(0.5);

7. Use Alternative PDF Libraries

If the issue persists, consider libraries like FPDF, DOMPDF, or mPDF, which may handle large datasets more efficiently.

Conclusion

By following these strategies, you can prevent TCPDF from exhausting memory and improve the performance when generating PDFs for large datasets.