Defining a Function
To define a function, use the following syntax:
function [&]function_name
( [parameter
[, ... ] ] ) { statement list }
The statement list can include
HTML. You can declare a PHP function
that doesn’t contain any PHP code. For instance, the
column( )
function simply gives a convenient
short name to HTML code that may be needed many times throughout the
page:
<? function column( ) { ?> </td><td> <? } ?>
The function name can be any string that starts with a letter or
underscore followed by zero or more letters, underscores, and digits.
Function names are
case-insensitive; that is, you
can call the sin( )
function as
sin(1)
, SIN(1)
,
SiN(1)
, and so on, because all these names refer
to the same function.
Typically,
functions return some value. To return a
value from a function, use the
return
statement: put return
expr
inside your function. When a
return
statement is encountered during execution,
control reverts to the calling statement, and the evaluated results
of expr
will be returned as the value of
the function. Although it can make for messy code, you can actually
include multiple return
statements in a function
if it makes sense (for example, if you have a
switch
statement to determine which of several
values to return).
If you define your function with the optional ampersand before the name, the function returns a reference to the returned data rather than a copy of the data.
Let’s take a look at a simple function. Example 3-1 takes two strings, concatenates ...
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