342 lines
14 KiB
HTML
342 lines
14 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>FAQ</title>
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<link type="text/css" rel="stylesheet" href="fpdf.css">
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<style type="text/css">
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ul {list-style-type:none; margin:0; padding:0}
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ul#answers li {margin-top:1.8em}
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.question {font-weight:bold; color:#900000}
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</style>
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</head>
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<body>
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<h1>FAQ</h1>
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<ul>
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<li><b>1.</b> <a href='#q1'>What's exactly the license of FPDF? Are there any usage restrictions?</a></li>
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<li><b>2.</b> <a href='#q2'>When I try to create a PDF, a lot of weird characters show on the screen. Why?</a></li>
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<li><b>3.</b> <a href='#q3'>I try to generate a PDF and IE displays a blank page. What happens?</a></li>
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<li><b>4.</b> <a href='#q4'>I can't make line breaks work. I put \n in the string printed by MultiCell but it doesn't work.</a></li>
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<li><b>5.</b> <a href='#q5'>I try to display a variable in the Header method but nothing prints.</a></li>
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<li><b>6.</b> <a href='#q6'>I defined the Header and Footer methods in my PDF class but nothing appears.</a></li>
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<li><b>7.</b> <a href='#q7'>Accented characters are replaced by some strange characters like é.</a></li>
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<li><b>8.</b> <a href='#q8'>I try to display the Euro symbol but it doesn't work.</a></li>
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<li><b>9.</b> <a href='#q9'>I get the following error when I try to generate a PDF: Some data has already been output, can't send PDF file</a></li>
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<li><b>10.</b> <a href='#q10'>I draw a frame with very precise dimensions, but when printed I notice some differences.</a></li>
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<li><b>11.</b> <a href='#q11'>I'd like to use the whole surface of the page, but when printed I always have some margins. How can I get rid of them?</a></li>
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<li><b>12.</b> <a href='#q12'>How can I put a background in my PDF?</a></li>
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<li><b>13.</b> <a href='#q13'>How can I set a specific header or footer on the first page?</a></li>
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<li><b>14.</b> <a href='#q14'>I'd like to use extensions provided by different scripts. How can I combine them?</a></li>
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<li><b>15.</b> <a href='#q15'>How can I send the PDF by email?</a></li>
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<li><b>16.</b> <a href='#q16'>What's the limit of the file sizes I can generate with FPDF?</a></li>
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<li><b>17.</b> <a href='#q17'>Can I modify a PDF with FPDF?</a></li>
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<li><b>18.</b> <a href='#q18'>I'd like to make a search engine in PHP and index PDF files. Can I do it with FPDF?</a></li>
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<li><b>19.</b> <a href='#q19'>Can I convert an HTML page to PDF with FPDF?</a></li>
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<li><b>20.</b> <a href='#q20'>Can I concatenate PDF files with FPDF?</a></li>
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</ul>
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<ul id='answers'>
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<li id='q1'>
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<p><b>1.</b> <span class='question'>What's exactly the license of FPDF? Are there any usage restrictions?</span></p>
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FPDF is released under a permissive license: there is no usage restriction. You may embed it
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freely in your application (commercial or not), with or without modifications.
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</li>
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<li id='q2'>
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<p><b>2.</b> <span class='question'>When I try to create a PDF, a lot of weird characters show on the screen. Why?</span></p>
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These "weird" characters are in fact the actual content of your PDF. This behavior is a bug of
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IE6. When it first receives an HTML page, then a PDF from the same URL, it displays it directly
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without launching Acrobat. This happens frequently during the development stage: on the least
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script error, an HTML page is sent, and after correction, the PDF arrives.
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<br>
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To solve the problem, simply quit and restart IE. You can also go to another URL and come
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back.
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<br>
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To avoid this kind of inconvenience during the development, you can generate the PDF directly
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to a file and open it through the explorer.
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</li>
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<li id='q3'>
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<p><b>3.</b> <span class='question'>I try to generate a PDF and IE displays a blank page. What happens?</span></p>
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First of all, check that you send nothing to the browser after the PDF (not even a space or a
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carriage return). You can put an exit statement just after the call to the Output() method to
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be sure. If it still doesn't work, it means you're a victim of the "blank page syndrome". IE
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used in conjunction with the Acrobat plug-in suffers from many bugs. To avoid these problems
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in a reliable manner, two main techniques exist:
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<br>
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<br>
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- Disable the plug-in and use Acrobat as a helper application. To do this, launch Acrobat, go
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to the Edit menu, Preferences, Internet, and uncheck "Display PDF in browser". Then, the next
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time you load a PDF in IE, it displays the dialog box "Open it" or "Save it to disk". Uncheck
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the option "Always ask before opening this type of file" and choose Open. From now on, PDF files
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will open automatically in an external Acrobat window.
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<br>
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The drawback of the method is that you need to alter the client configuration, which you can do
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in an intranet environment but not for the Internet.
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<br>
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<br>
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- Use a redirection technique. It consists in generating the PDF in a temporary file on the server
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and redirect the client to it. For example, at the end of the script, you can put the following:
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<div class="doc-source">
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<pre><code>//Determine a temporary file name in the current directory
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$file = basename(tempnam('.', 'tmp'));
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rename($file, $file.'.pdf');
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$file .= '.pdf';
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//Save PDF to file
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$pdf->Output($file, 'F');
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//Redirect
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header('Location: '.$file);</code></pre>
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</div>
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This method turns the dynamic PDF into a static one and avoids all troubles. But you have to do
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some cleaning in order to delete the temporary files. For example:
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<div class="doc-source">
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<pre><code>function CleanFiles($dir)
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{
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//Delete temporary files
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$t = time();
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$h = opendir($dir);
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while($file=readdir($h))
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{
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if(substr($file,0,3)=='tmp' && substr($file,-4)=='.pdf')
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{
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$path = $dir.'/'.$file;
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if($t-filemtime($path)>3600)
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@unlink($path);
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}
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}
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closedir($h);
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}</code></pre>
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</div>
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This function deletes all files of the form tmp*.pdf older than an hour in the specified
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directory. You may call it where you want, for example in the script which generates the PDF.
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</li>
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<li id='q4'>
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<p><b>4.</b> <span class='question'>I can't make line breaks work. I put \n in the string printed by MultiCell but it doesn't work.</span></p>
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You have to enclose your string with double quotes, not single ones.
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</li>
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<li id='q5'>
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<p><b>5.</b> <span class='question'>I try to display a variable in the Header method but nothing prints.</span></p>
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You have to use the <code>global</code> keyword to access global variables, for example:
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<div class="doc-source">
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<pre><code>function Header()
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{
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global $title;
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$this->SetFont('Arial', 'B', 15);
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$this->Cell(0, 10, $title, 1, 1, 'C');
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}
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$title = 'My title';</code></pre>
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</div>
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Alternatively, you can use an object property:
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<div class="doc-source">
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<pre><code>function Header()
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{
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$this->SetFont('Arial', 'B', 15);
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$this->Cell(0, 10, $this->title, 1, 1, 'C');
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}
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$pdf->title = 'My title';</code></pre>
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</div>
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</li>
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<li id='q6'>
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<p><b>6.</b> <span class='question'>I defined the Header and Footer methods in my PDF class but nothing appears.</span></p>
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You have to create an object from the PDF class, not FPDF:
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<div class="doc-source">
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<pre><code>$pdf = new PDF();</code></pre>
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</div>
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</li>
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<li id='q7'>
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<p><b>7.</b> <span class='question'>Accented characters are replaced by some strange characters like é.</span></p>
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Don't use UTF-8 encoding. Standard FPDF fonts use ISO-8859-1 or Windows-1252.
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It is possible to perform a conversion to ISO-8859-1 with utf8_decode():
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<div class="doc-source">
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<pre><code>$str = utf8_decode($str);</code></pre>
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</div>
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But some characters such as Euro won't be translated correctly. If the iconv extension is available, the
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right way to do it is the following:
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<div class="doc-source">
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<pre><code>$str = iconv('UTF-8', 'windows-1252', $str);</code></pre>
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</div>
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</li>
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<li id='q8'>
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<p><b>8.</b> <span class='question'>I try to display the Euro symbol but it doesn't work.</span></p>
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The standard fonts have the Euro character at position 128. You can define a constant like this
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for convenience:
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<div class="doc-source">
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<pre><code>define('EURO', chr(128));</code></pre>
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</div>
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</li>
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<li id='q9'>
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<p><b>9.</b> <span class='question'>I get the following error when I try to generate a PDF: Some data has already been output, can't send PDF file</span></p>
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You must send nothing to the browser except the PDF itself: no HTML, no space, no carriage return. A common
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case is having extra blank at the end of an included script file.<br>
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If you can't figure out where the problem comes from, this other message appearing just before can help you:<br>
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<br>
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<b>Warning:</b> Cannot modify header information - headers already sent by (output started at script.php:X)<br>
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<br>
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It means that script.php outputs something at line X. Go to this line and fix it.
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In case the message doesn't show, first check that you didn't disable warnings, then add this at the very
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beginning of your script:
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<div class="doc-source">
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<pre><code>ob_end_clean();</code></pre>
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</div>
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If you still don't see it, disable zlib.output_compression in your php.ini and it should appear.
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</li>
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<li id='q10'>
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<p><b>10.</b> <span class='question'>I draw a frame with very precise dimensions, but when printed I notice some differences.</span></p>
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To respect dimensions, select "None" for the Page Scaling setting instead of "Shrink to Printable Area" in the print dialog box.
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</li>
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<li id='q11'>
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<p><b>11.</b> <span class='question'>I'd like to use the whole surface of the page, but when printed I always have some margins. How can I get rid of them?</span></p>
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Printers have physical margins (different depending on the models); it is therefore impossible to remove
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them and print on the whole surface of the paper.
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</li>
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<li id='q12'>
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<p><b>12.</b> <span class='question'>How can I put a background in my PDF?</span></p>
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For a picture, call Image() in the Header() method, before any other output. To set a background color, use Rect().
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</li>
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<li id='q13'>
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<p><b>13.</b> <span class='question'>How can I set a specific header or footer on the first page?</span></p>
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Simply test the page number:
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<div class="doc-source">
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<pre><code>function Header()
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{
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if($this->PageNo()==1)
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{
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//First page
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...
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}
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else
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{
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//Other pages
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...
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}
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}</code></pre>
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</div>
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</li>
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<li id='q14'>
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<p><b>14.</b> <span class='question'>I'd like to use extensions provided by different scripts. How can I combine them?</span></p>
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Use an inheritance chain. If you have two classes, say A in a.php:
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<div class="doc-source">
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<pre><code>require('fpdf.php');
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class A extends FPDF
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{
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...
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}</code></pre>
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</div>
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and B in b.php:
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<div class="doc-source">
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<pre><code>require('fpdf.php');
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class B extends FPDF
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{
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...
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}</code></pre>
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</div>
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then make B extend A:
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<div class="doc-source">
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<pre><code>require('a.php');
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class B extends A
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{
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...
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}</code></pre>
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</div>
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and make your own class extend B:
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<div class="doc-source">
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<pre><code>require('b.php');
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class PDF extends B
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{
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...
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}
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$pdf = new PDF();</code></pre>
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</div>
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</li>
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<li id='q15'>
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<p><b>15.</b> <span class='question'>How can I send the PDF by email?</span></p>
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As any other file, but an easy way is to use <a href="http://phpmailer.codeworxtech.com">PHPMailer</a> and
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its in-memory attachment:
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<div class="doc-source">
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<pre><code>$mail = new PHPMailer();
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...
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$doc = $pdf->Output('', 'S');
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$mail->AddStringAttachment($doc, 'doc.pdf', 'base64', 'application/pdf');
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$mail->Send();</code></pre>
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</div>
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</li>
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<li id='q16'>
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<p><b>16.</b> <span class='question'>What's the limit of the file sizes I can generate with FPDF?</span></p>
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There is no particular limit. There are some constraints, however:
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<br>
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<br>
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- The maximum memory size allocated to PHP scripts is usually 8MB. For very big documents,
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especially with images, this limit may be reached (the file being built into memory). The
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parameter is configured in the php.ini file.
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<br>
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<br>
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- The maximum execution time allocated defaults to 30 seconds. This limit can of course be easily
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reached. It is configured in php.ini and may be altered dynamically with set_time_limit().
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<br>
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<br>
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- Browsers generally have a 5 minute time-out. If you send the PDF directly to the browser and
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reach the limit, it will be lost. It is therefore advised for very big documents to
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generate them in a file, and to send some data to the browser from time to time (with a call
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to flush() to force the output). When the document is finished, you can send a redirection to
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it or create a link.
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<br>
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Remark: even if the browser times out, the script may continue to run on the server.
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</li>
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<li id='q17'>
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<p><b>17.</b> <span class='question'>Can I modify a PDF with FPDF?</span></p>
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It is possible to import pages from an existing PDF document thanks to the FPDI extension:<br>
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<br>
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<a href="http://www.setasign.de/products/pdf-php-solutions/fpdi/" target="_blank">http://www.setasign.de/products/pdf-php-solutions/fpdi/</a><br>
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<br>
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You can then add some content to them.
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</li>
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<li id='q18'>
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<p><b>18.</b> <span class='question'>I'd like to make a search engine in PHP and index PDF files. Can I do it with FPDF?</span></p>
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No. But a GPL C utility does exist, pdftotext, which is able to extract the textual content from
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a PDF. It is provided with the Xpdf package:<br>
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<br>
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<a href="http://www.foolabs.com/xpdf/" target="_blank">http://www.foolabs.com/xpdf/</a>
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</li>
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<li id='q19'>
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<p><b>19.</b> <span class='question'>Can I convert an HTML page to PDF with FPDF?</span></p>
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Not real-world pages. But a GPL C utility does exist, htmldoc, which allows to do it and gives good results:<br>
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<br>
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<a href="http://www.htmldoc.org" target="_blank">http://www.htmldoc.org</a>
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</li>
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<li id='q20'>
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<p><b>20.</b> <span class='question'>Can I concatenate PDF files with FPDF?</span></p>
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Not directly, but it is possible to use <a href="http://www.setasign.de/products/pdf-php-solutions/fpdi/demos/concatenate-fake/" target="_blank">FPDI</a>
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to perform this task. Some free command-line tools also exist:<br>
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<br>
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<a href="http://thierry.schmit.free.fr/spip/spip.php?article15&lang=en" target="_blank">mbtPdfAsm</a><br>
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<a href="http://www.accesspdf.com/pdftk/" target="_blank">pdftk</a>
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</li>
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</ul>
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</body>
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</html>
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