There are already many functions built into PHP. However, you
can define your own and organize your code into functions. To define your own
functions, start out with the function statement:
function some_function([arguments]) { code to execute }
The brackets ([ ]) mean optional. The code could also
be written with optional_arguments in place of
[arguments]. The function keyword is
followed by the name of the function. Function names abide by the same rules as
other named objects such as variables in PHP. A pair of parentheses must come
next. If your function has parameters, they're specified within the parentheses.
Finally, the code to execute is listed between curly brackets, as seen in the
code above.
You can define functions anywhere in your code and call them
from virtually anywhere. Scope rules apply. The scope of a variable is the
context within which it's defined. For the most part, all PHP variables have
only a single scope. A single scope spans included and required files as well.
The function is defined on the same page or included in an include file.
Functions can have parameters and return values that allow you to reuse
code.
To create your own function that simply displays a different
hello message, you would write:
<?php function hi() { echo ("Hello from function-land!"); } //Call the function hi(); ?>
which displays:
Hello from function-land!