PHP Troubleshooting

• My PHP page is completely empty when viewed through the browser
  This means that either you have a syntax error or there is something wrong with permissions. To check for syntax errors in "filename.php", you can do two things. Either run php -n filename.php on the command-line or create a second script in the same directory:
  

  <?php
   error_reporting(E_ALL);
   ini_set("display_errors", 1);
   include("filename.php");
  ?>
  

  Execute that second script. If permissions are ok and there are no syntax errors, do "View page source".
• Im a getting a "500 INTERNAL SERVER ... is writeable by group" error.
  For security reasons on socweb the file permissions for PHP files must be chmod 755, not chmod 777.
• It doesn't work, but it doesn't produce an error either.
  Have a look at the source of the page via your browser ("View source" or "View page source") for more details. Also: Turn error reporting on. Add "error_reporting(E_ALL);" in the line after your first "<?php". Some of the errors it shows are just warnings that you can ignore. But it might give you more hints about the problem.
• Invisible control characters
  If you copy and paste code on a PC, you sometimes encounter some invisible control characters because of the differences between PCs and Unix and because of different character encodings. Use the UltraEdit editor that is installed in the JKCC instead of Notepad. If you still have problems with UltraEdit, use nano on Socweb. Copy and paste your code into UltraEdit or nano, save it and try running it again.
• What editor should I use
  On a PC in the JKCC: UltraEdit. On Socweb: nano or any other standard Unix editor that is installed.
• How do I combine PHP and XML
  All code outside <?php ... > needs to be XML (or HTML) tags.
  All code inside <?php ... > needs to be echo statements or other PHP commands.
  For example, see the answer to exercise 5 from Week 3.
• What if "View page source" shows the <?php ...> tags
  This means that the webserver has not executed your PHP code.
  • Are you using the correct URL in your browser? (A URL starting with "I:\" is wrong.)
  • Make sure that your PC doesn't save the PHP files with extension ".txt".
  • If your script is producing SVG or XML output, make sure that there isn't a blank line at the beginning of the script and the very first command is creating the correct header.
  If that's not the problem, see the comment about invisible control characters above.
• I copied and pasted code from the exercise pages or the answers, but it does not work
  All of the code examples have been tested on Socweb. Most likely your problem is due to invisible control characters or permissions (see the questions above). If you are absolutely sure that that isn't the problem, send an email to me (u.priss) detailing the problem.
• I get an error with a line number pointing to the end of the file
  This means you forgot to close some string or expression. Check whether all your opening brackets have closing brackets. Check your quotes (see the question about nesting quotes below).
• I get an error, which doesn't look like a normal PHP error
  This could be an XML error. Check whether the syntax of your XML code is correct. Are all attributes quoted? Do you have closing tags?
• How do I nest quotes?
  Long echo statements should be avoided because it can be difficult to keep track of quotes. It is best to use single quotes for XML attributes and double quotes for echo. In that manner you can include XML tags within echo statements. You can include double quotes within double quotes if you escape them by placing backslashes in front of the inner quotes.
• $_REQUEST[...] and $_POST[...] are not working
  For some reason POST is disabled by C&IT for some students. Please, use GET in your forms, if POST does not work.
• My own HTML pages have stopped working
  For some reason C&IT seems to occasionally reset permissions. Go to your home directory (the one above public_html) and type "chmod 711 .".

Questions about the coursework