README

Merge multiple PDF files into a single PDF using Ghostscript.

This library uses the Ghostscript CLI to efficiently merge PDF files on Linux or any environment where Ghostscript is installed.

Why this library?

There are many PDF merger libraries out there, but most rely on FPDI, which has limitations in its free version—especially when dealing with certain types of PDFs.

We created pdf-merger as a simple alternative that uses Ghostscript instead, offering a reliable and unrestricted solution for merging PDFs without those limitations.

Requirements

• PHP 5.6 or above
• Ghostscript CLI (gs command)

Installation

composer require ngekoding/pdf-merger

Usage

Simple usage

<?php

require 'vendor/autoload.php';

use Ngekoding\PdfMerger\PdfMerger;

$merger = new PdfMerger();
$merger->addFiles([
    'file1.pdf',
    'file2.pdf',
    'file3.pdf'
]);

$output = $merger->merge();

echo "Merged PDF created at: $output\n";

Adding files one by one

$merger = new PdfMerger();
$merger->addFile('file1.pdf');
$merger->addFile('file2.pdf');
$output = $merger->merge();

Setting custom output folder and filename

By default, the merged PDF will be saved in your system's temp directory with a timestamped filename.

You can customize the output folder and/or filename:

$merger = new PdfMerger();
$merger->addFiles(['file1.pdf', 'file2.pdf']);
$merger->setOutputFolder('/path/to/output/folder');
$merger->setOutputFilename('merged-result.pdf');
$output = $merger->merge();

Setting output file directly

Instead of setting output folder and filename separately, you can set the full output file path directly:

$merger = new PdfMerger();
$merger->addFiles(['file1.pdf', 'file2.pdf']);
$merger->setOutputFile('/path/to/output/merged.pdf');
$output = $merger->merge();

Setting Ghostscript executable path

If gs is not in your system PATH or you want to use a custom Ghostscript binary:

$merger = new PdfMerger();
$merger->setGsPath('/usr/local/bin/gs');

Setting compression level

You can choose one of the predefined Ghostscript compression levels using the setCompressionLevel() method. The library provides constants for convenience:

use Ngekoding\PdfMerger\CompressionLevel;

$merger = new PdfMerger();
$merger->setCompressionLevel(CompressionLevel::SCREEN);   // Lower quality, smaller size
$merger->setCompressionLevel(CompressionLevel::EBOOK);    // Medium quality
$merger->setCompressionLevel(CompressionLevel::PRINTER);  // High quality for printing
$merger->setCompressionLevel(CompressionLevel::PREPRESS); // Highest quality with color profiles
$merger->setCompressionLevel(CompressionLevel::DEFAULT);  // Balanced default
$merger->setCompressionLevel(CompressionLevel::NONE);     // No compression – closest to original

Note: Using CompressionLevel::NONE will skip the -dPDFSETTINGS parameter entirely, resulting in output that is as close as possible to the original quality.

For more technical details, you can refer to the Ghostscript documentation.

Setting process timeout

By default, the Ghostscript process timeout is 60 seconds. You can change it (in seconds) or disable by passing null:

$merger->setTimeout(120);  // 2 minutes timeout

Resetting the merger instance

You can reset the internal state (input files, output settings, compression, etc.) to start fresh:

$merger = new PdfMerger();
$merger->addFiles(['file1.pdf', 'file2.pdf']);
$merger->setOutputFile('/path/to/output/merged.pdf');
$output = $merger->merge();

// Reset the instance to merge other files
$merger->reset();

$merger->addFiles(['file3.pdf', 'file4.pdf']);
$output2 = $merger->merge();

Notes

• At least two PDF files are required for merging.
• The library throws exceptions on errors — use try-catch blocks for error handling in production.

License

This project is open-sourced under the MIT license.