Description:
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I am using a catpha script on my site. The script works fine at home (EasyPHP 2 on WinXP). Once I upload to a host server, I get the error, given below. The code was obtained from a captcha plugin for Dreamweaver.

I have created a file with phpinfo(); at: http://smartpetitions.com/info.php

The page is:
http://smartpetitions.com/create.php

I have checked the reported bugs:
http://bugs.php.net/bug.php?id=19542
http://bugs.php.net/bug.php?id=21028

Reproduce code:
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<?php // create.php
//...MISSING CODE..
function CaptchaImage($width='120',$height='30',$characters='6',$hex_bg_color='FFFFFF',$hex_text_color="FF0000",$hex_noise_color="CC0000", $img_file='captcha.jpg') {
  //...MISSING CODE..
  /* create textbox and add text */
  $textbox = imagettfbbox($font_size, 0, $this->font, $code); // LINE 57
  $x = ($width - $textbox[4])/2;
  $y = ($height - $textbox[5])/2;
  imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code);
  /* save the image */
  //...MISSING CODE..
}
?>
<!-----MISSING CODE----------->
<td><div style="border:1px solid gray; padding:5px 5px; width:200px; text-align:center;">
  <?php $captcha = new CaptchaImage(150,50,5,'FFFFFF','003366','0099CC');?> 
  <img src="/images/refresh.gif" title="Refresh Code" onclick="captcha()" /><br />
  <div style="padding:4px 0px;">Enter the code and click 'Create':</div>
<!-----MISSING CODE----------->

Expected result:
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Just like this page. A verification code. The code on the page works fine when tested offline on EasyPHP, Wamp or Xampp, on multiple PC's.

Actual result:
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Fatal error: Call to undefined function imagettfbbox() in /home/smartpet/public_html/create.php on line 57