PDF_info_textline()

(PECL pdflib >= 2.1.0)

Perform textline formatting and query metrics

说明

PDF_info_textline(resource $pdfdoc,string $text,string $keyword,string $optlist):float

Performs textline formatting and queries the resulting metrics.

You can use PDF_info_textline to center some text in the page.
Here's a little function
<?php
// Parameters:
// $p -> the PDF handle
// $text -> the text to center
// $posy -> the vertical position of the text
// $pageWidth -> the width of the page, defaults to 595 (A4)
function center_text($p, $text, $posy, $pageWidth=595)
  {
  $width = PDF_info_textline($p, $text, 'width', '');
  PDF_fit_textline($p, $text, ($pageWidth-$width)/2, $posy, '');
}
?>