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Chapter 8
Reusing PHP Code
In This Chapter
Including files in scripts
Understanding security for included files
Writing functions
Using functions
O
ften scripts need to perform the same actions in several different loca-
tions in the script. For example, a script may need to get data from a
database several different times. It may even be the case that you use the
same code in different scripts. If you find yourself typing the same ten lines of
code over and over (or cutting and pasting it repeatedly), you can move that
code into a separate file and get it from that file whenever you need it. Here
are several reasons to reuse code:
Less typing:Less work is always a good reason for anything.
Debug once:You can write the code once, debug it so you know it works,
and then use it whenever you need it. It’s rare to write code that doesn’t
have a typo or two in it, let alone occasional peculiar logic, so code always
has to be debugged. It saves time to use proven code when possible,
instead of writing new code that will have to be debugged.
Easier to understand:A shorter script that is less cluttered with code is
easier for people to read and understand. For example, one line in your
script that says
getData()
is easier to understand than the ten lines
that actually get the data.
Easier to maintain:If you reuse code and you need to change something
in the code, you only need to change it in one external file, instead of
having to find and change it in a dozen places in your script. For exam-
ple, if you change the name of your database, you can change the name
in one file, rather than having to change it repeatedly in many scripts.
You can reuse code two ways: by inserting a file containing code into a script
or by writing and calling a function. In this chapter, you find out how to use
both methods.
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