I’m going back to the basics here, you know, when you wrote your first PHP script and saw an ugly-ass error message pop up on your screen? Error messages are the best tool a programmer has.
Set up Error Reporting
Most PHP errors are straight forward, but there are times where you don’t see any which makes it very difficult to tell what the problem is.
The first step of PHP troubleshooting is to turn error reporting on. For security reasons you’ll want error reporting off by default, but if something goes wrong you’ll need the information for debugging. You can usually enable error reporting by adding this line to the problem script:
<?php error_reporting(E_ALL) ?>
Or you can add these lines to the root .htaccess:
php_flag display_errors on
php_value error_reporting 6143
This will usually display an error useful for troubleshooting, that is, if the software and your server configuration allows it.
Parse Errors
Parse error: parse error, unexpected T_STRING in……
This is a syntax error. Perhaps you forgot a semi-colon at the end of a line, or you forgot a double quote (“) or an end bracket (}) after you started one. For quote and semicolon issues, the problem is usually the line above the one reported in the error. For brackets, it may be at the end of the script.
Parse error: syntax error, unexpected $end in
You’re most likely missing a } somewhere. Make sure that each { you have is also closed with a }.
Parse error: syntax error, unexpected T_STRING, expecting ‘,’ or ‘;’ in..
There may be double quotes within double quotes. They either need to be escaped or brought to single quotes. It’s also possible that a new PHP statement was started before the previous was finished.
Header Errors
Warning: Cannot add header information – headers already sent by (output started at /home/vnessa5/www/errors.php:9) in….
Warning: Cannot send session cache limiter – headers already sent in somefile.php on line 222
Naturally, HTML will parse before PHP. The script is trying to send header information after you’ve already sent output to the browser. HTTP headers are required to be sent before any output from your script, which means that a header function must be placed before any html or even a white space. There are two solutions for this. Either (1) Set the header tags the top of the document, or (2) insert a header redirect by adding this to the very top of the page to force the output buffer:
<?php ob_start();
Then this at the very end of the page (not usually required)
ob_end_flush(); ?>
mySQL Result Source Errors
Warning: Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in…
You need to take a look at the $result variable used to define the loop. More than likely there is a syntax error on the reported line before the $result field, or the value of $result does not exist.
Supplied argument is not a valid stream resource…
This is usually caused when your code is looking for a table or other resource in the database that does not exist.
Sessions are not being created or maintained
This can apply to any of the scenarios below:
(1) The program isn’t remembering your login
(2) Your shopping cart won’t hold items
(3) Your php script is redirecting like crazy
(4) “Call undefined function session_start” error
(5) PHP isn’t processing pages called by something like index.php?page=home&id=7
Your site is most likely dependent on register_globals. You can enable them by putting this line in your .htaccess (or just enabling in your php.ini if you have access):
php_flag register_globals On
Stream Errors
Warning: failed to open stream…
Warning: main(/index.php): failed to open stream: No such file or directory in…
This is usually because either the specified file is missing, or a file declared in a require() or include() function is missing. The easiest way to fix this is by re-installing the PHP program from a freshly-uploaded copy, or restoring the original config.php and just changing the db information. The include path may also be incorrect, but either way your script is looking for a file that isn’t there, or it is looking in the wrong place.
Warning: fopen(…): failed to open stream: Permission denied in…
This is a permissions and/or ownership issue. Try first setting the permissions to 777 just to see if the script will run. If so, you should narrow down the permissions to 775. If not, set the user/group to user:nobody.
Warning: <…> is not a valid stream resource…
Warning: fread(): supplied argument is not a valid stream resource in…
This is an error seen when trying to use functions like fopen(), fread(), feof(), etc. and are usually caused by an invalid or unavailable resource that is being called in the line specified. For instance, if the fread() function is returning this error, it could be that the file it is trying to access does not have the correct permissions or does not exist.
Warning: Failed opening….
Warning: Failed opening ‘…’ for inclusion (include_path=’.:/usr/local/lib/php’) in Unknown on line 0
Make the sure that the file mentioned (and its holding directorie) has read + execute permissions, and that the path to the file is correct. If not, you’ll need to add the path into the PHP code: (or .htaccess)
include(“/path/to/files”);
Blank PHP Pages
You go to a .php page, but it’s blank.
The scope of what can cause blank pages is very broad, but there are a few things to look at:
-Is error reporting turned off anywhere in the script or in the .htaccess? If so, turn it on to see what is happening (php_flag display_errors on), or add the lines at the top of this page into the script.
-Is the PHP script even generating any output (usually you can tell my finding the print function?
-Check the database connection, i.e, username, dbname, user added to db, etc.
-Try using the full <?PHP ?> tags, rather than the shorter versions <? ?>
Also, if the software is prebundled (like phpBB or Gallery), then the index or one of the include pages could be corrupted. Usually you can just replace the problem page with a working version from another installation.
Max Execution Time Error
You receive some variant of a “Max_execution_time” error when loading a page.
This is caused when a PHP script takes longer to execute than the server allows, but can be adjusted by adding a PHP directive to your .htaccess: (in seconds, 0 = unlimited) or modifying the value in php.ini.
php_value max_execution_time 0
Open_basedir Errors
Warning: Unknown(): open_basedir restriction in effect.
This is a protective feature of Apache that restricts PHP from accessing files/folders outside the user’s home directory. Most of the time this is due to an incorrect include path in one or more of the config files (which are usually mentioned). Look for something like this:
/includes/somefile.php
/admin/files/anotherfile.php
The heading / tells the filesystem that these folders are on the server root, and thus prevents PHP from accessing them. You can usually fix this by changing the path to these files to be absolute to their location:
/home/username/public_html/includes/somefile.php
or
./includes/somefile.php
