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

Exceptions in Bob’s Auto Parts
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This example is fairly simple. In the next section, we look at ways to create different
exceptions to deal with different categories of error.
Exceptions in Bob’s Auto Parts
Chapter 2,“Storing and Retrieving Data,” described how you could store Bob’s order
data in a flat file.You know that file I/O (in fact, any kind of I/O) is one area in programs
where errors often occur.This makes it a good place to apply exception handling.
Looking back at the original code, you can see that three things are likely to go
wrong with writing to the file: the file cannot be opened, a lock cannot be obtained, or
the file cannot be written to.We created an exception class for each of these possibilities.
The code for these exceptions is shown in Listing 7.4.
Listing 7.4