The "call to undefined imagecreate() function" normally appears if you try to execute graphic related scripts such as CAPTCHA scripts. To fix this problem, follow these simple steps:
1. Download a copy of PHP zip package from http://php.net/downloads.php.
2. For the sake of example, we will be using PHP 5.2.14 Windows Binary Zip Package.
3. Once you have downloaded the file, Right-Click it>Extract files>In the Winrar Destination path, enter “C:\PHP\” no quotes. If you have previously installed PHP distros just overwrite it.(I’ve assumed here that you have Winrar installed on your computer.)
4. Go to where your PHP file was extracted, in this case in the C:\ directory.
5. Locate php.ini-dist and rename it to php.ini.(Overwite the previous php.ini).
6. Right-click php.ini>Select Open. The following should then appear:
7. Click Edit>Select Find then enter extension_dir in the Find what textbox.
8. Change the line extension_dir=”./” to extension_dir=”C:\PHP\ext”.
9. Click Edit>Find>Enter “gd”(no quotes) in the Find what textbox then click Find Next.
10. Delete the semi-colon(;) before the line ;extension=php_gd2.dll.
11. Click File the Save. You should now be able to execute your captcha scripts without errors. Here is the screenshot of my captcha that I was able to execute effortlessly using these fixes:
12. If you continue to encounter error messages, try restarting your computer.
13. That's all. Ciao!