PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

Programming Errors
553
run into this problem with single and double quotation marks and also with the various
forms of brackets and parentheses.
The following script generates a similar syntax error:
These errors can be hard to find if they result from a combination of multiple files.They
can also be difficult to find if they occur in a large file. Seeing parse error on
line 1001 of a 1000-line file can be enough to spoil your day, but it should provide a
subtle hint that you should try to write more modular code.
In general, though, syntax errors are the easiest type of error to find. If you make a
syntax error and try to execute that block of code, PHP will give you a message telling
you where to find your mistake.
Runtime Errors
Runtime errors can be harder to detect and fix. A script either contains a syntax error, or
it does not. If the script contains a syntax error, the parser will detect it when that code
is executed. Runtime errors are not caused solely by the contents of your script.They
can rely on interactions between your scripts and other events or conditions.
The statement
require ('filename.php');
is a perfectly valid PHP statement. It contains no syntax errors.
This statement might, however, generate a runtime error. If you execute this statement
and filename.php does not exist or the user who the script runs as is denied read
permission, you will get an error resembling this one:
Fatal error: main() [function.require]: Failed opening required 'filename.php'
(include_path='.:/usr/local/lib/php') in
/home/book/public_html/phpmysql4e/chapter26/error.php on line 1
Although nothing is wrong with the code here, because it relies on a file that might or
might not exist at different times when the code is run, it can generate a runtime error.
The following three statements are all valid PHP. Unfortunately, in combination, they
attempt to do the impossible—divide by zero:
$i = 10;
$j = 0;
$k = $i/$j;
This code snippet generates the following warning:
Warning: Division by zero in
/home/book/public_html/phpmysql4e/chapter26/div0.php on line 3