Functions The real power of PHP: more than 700 built-in
functions. To keep the browser from executing a script when the
page loads, you can put your script into a function. A function
will be executed by a call to the function. You may call a function
from anywhere within a page.
Slide 3
Create a PHP Function A function will be executed by a call to
the function. function functionName() { code to be executed; }
Slide 4 ">
Adding parameters "; } echo "My name is "; writeName("Kai
Jim"); echo "My sister's name is "; writeName("Hege"); echo "My
brother's name is "; writeName("Stale"); ?>
Slide 5
Return values
Slide 6
Common error I: invoking an undefined function function
output_paragraph( $text ) { echo " {$text} "; } outputParagraph(
'Today is '. Date('d/m/y') );
Slide 7
Common error II: scope function get_circle_area() { return 3.14
* $radius * $radius; } $radius = 5; $area = get_circle_area(); echo
" The area of the circle is {$area} ";
Slide 8
function get_circle_circumference( $diameter ) { $circumference
= 3.14 * $diameter; } echo ' '; echo 'The circumference is ';
get_circle_circumference( 10 ); echo $circumference; echo ' ';
Slide 9
Variables in PHP If you do not use functions, any variables you
create can be used anywhere in your script But if you define your
own functions, you must distinguish four kinds of variable a
function's formal parameters a function's local variables your
script's global variables PHP's superglobal variables These differ
in where they are created which hence determines their scope The
scope of a variable is the range of statements in the program in
which the variable's name is known
Slide 10
Formal parameters and local variables A function's formal
parameters as we know, these are created when the function is
invoked scope: the function's body A function's local variables
variables which are created inside a function scope: from the
statement in which they are created to the end of the function's
body
Slide 11
Global variables and superglobal variables A script's global
variables variables which are created outside a function scope:
from the statement in which they are created to the end of the
script but not inside functions PHP's superglobal variables, e.g.
$_GET, $_POST as we have seen, these are special PHP variables
which you don't create scope: the whole script, both inside and
outside functions
Slide 12
What is the output? $x = 10; function func1() { echo $x; }
func1();