How to process PDF files using PHP

As a universal file format, PDF files are widely used in various application scenarios, such as e-books, reports, contracts, etc. During the development process, we often need to generate, edit, read and other operations on PDF files. As a scripting language, PHP can also easily complete these tasks. This article will introduce how to use PHP to process PDF files.

1. Generate PDF files

There are many ways to generate PDF files, the most common of which is to use the PDF library. The PDF library is a tool for generating PDF documents, which provides PDF document generation functions for PHP. The most commonly used PDF libraries in PHP are FPDF and TCPDF.

1. FPDF

FPDF is an open source PDF library based on PHP that allows users to dynamically generate PDF documents. FPDF is simple and easy to use, supports Chinese characters, and provides a variety of fonts and page layout settings.

The following is an example of using FPDF to generate a simple PDF document:

require('fpdf.php');

$pdf = new FPDF();
$pdf->AddPage();
$pdf->SetFont('Arial','B',16);
$pdf->Cell(40,10,'Hello World!');
$pdf->Output();

The above code uses the FPDF library to create a simple PDF document, sets the page font, size and content, and outputs to the browser. Execute the above code and you can see the generated PDF document in the browser.

2. TCPDF

TCPDF is another commonly used open source PDF library. Similar to FPDF, it also provides many features, such as Chinese character support, multiple fonts and page layouts. set up. Compared with FPDF, TCPDF is more powerful and provides more functional interfaces, such as setting watermarks, adding pictures, etc.

The following is an example of using TCPDF to generate a simple PDF document:

require_once('TCPDF/tcpdf.php');

$pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);

$pdf->SetCreator(PDF_CREATOR);
$pdf->SetAuthor('John Doe');
$pdf->SetTitle('TCPDF Example');
$pdf->SetSubject('TCPDF Tutorial');

$pdf->SetFont('dejavusans', '', 14);
$pdf->AddPage();
$pdf->Write(5, 'Hello World');

$pdf->Output('example.pdf', 'I');

The above code uses the TCPDF library to create a simple PDF document, setting the page properties, font, size and content. and output to the browser.

2. Edit PDF files

In actual development, we often need to edit existing PDF files, such as adding, deleting, moving and modifying page content. Although PHP itself cannot directly edit PDF files, it can be achieved with the help of some mature PDF libraries.

1. FPDI

FPDI is a PHP library that provides methods to import and reuse existing PDF documents. FPDI is able to read every page of a PDF and use it as a basis for subsequent editing or reuse.

The following is an example of using FPDI to read and jump to a PDF file page:

require_once('fpdf/fpdf.php');
require_once('fpdi/fpdi.php');

$pdf = new FPDI();
$pageCount = $pdf->setSourceFile("example.pdf");
$pageId = 1;
$templateId = $pdf->importPage($pageId);

$pdf->AddPage();
$pdf->useTemplate($templateId,0,0);

// 访问导入的文档中的信息
$textWidth = $pdf->GetStringWidth('Hello World');
$pdf->SetFont('Arial', null, 14);
$pdf->SetTextColor(255, 0, 0);
$pdf->SetXY(105 - $textWidth / 2, 130);
$pdf->Write(0, 'Hello World');

$pdf->Output('example.pdf','I');

The above code uses the FPDF library and calls the FPDI method to read an existing PDF document and jump to the specified page. Then, the font, text color and coordinates are set and output to the browser.

2. PDFlib

PDFlib is an advanced PDF generation library for PHP that allows users to dynamically generate, edit and output PDF files. PDFlib provides a rich set of features, supporting various text fonts, multiple image output formats, dynamic graphics and standard PDF elements.

The following is an example of using PDFlib to create a PDF document, add text, and store it:

$p = new PDFlib();

// 创建PDF文件
if ($p->begin_document("", "") == 0) {
    die("Error: " . $p->get_errmsg());
}

// 设置编码及页码
$p->set_info("Creator", "Hello World");
$p->set_info("Author", "John Doe");
$p->set_info("Title", "Hello World");

$p->begin_page_ext(595, 842, "");

// 加载字体
$font = $p->load_font("Helvetica", "winansi", "");

$p->setfont($font, 24.0);
$p->set_text_pos(50, 700);
$p->show("Hello, World!");

$p->end_page_ext("");
$p->end_document("");

// 保存到本地文件
file_put_contents("example.pdf", $p->get_buffer());

The above code uses the PDFlib library to create a new PDF document, add text, and then store it. to a local file.

3. Reading PDF files

Reading PDF files is a very important function. In many cases, we need to read the content in PDF files, such as generating reports, extracting data, etc. PHP provides many libraries to implement reading operations of PDF files.

1. pdftotext

pdftotext is a tool for converting PDF documents to text format. It can be called from PHP to get the text content of a PDF file.

The following is an example of using the pdftotext library to read a PDF document and extract text:

$text = shell_exec('pdftotext example.pdf -');
echo $text;

The above code uses the pdftotext library to read a PDF document and output its text content to the browser.

2. PDF Parser

PDF Parser is a PHP library that provides a way to extract content from existing PDF documents. PDF Parser is able to read all text content in PDF documents and convert them into an easy-to-process format.

The following is an example of using PDF Parser to read a PDF document and extract text:

require_once('vendor/autoload.php');

$parser = new SmalotPdfParserParser();
$pdf = $parser->parseFile('example.pdf');

$text = $pdf->getText();
echo $text;

The above code uses the PDF Parser library to read a PDF document and output its text content to the browser.

Summary

This article introduces how to use PHP to process PDF files. We learned to use the PDF library to generate PDF files, use FPDI and PDFlib to edit PDF files, and use pdftotext and PDF Parser to read PDF files. Although these methods cover many common PDF processing tasks, the PDF libraries and tools provided by PHP have more functions to be explored and mined. Readers can choose different methods to process PDF files according to their needs.

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