PHP
5 Functions
The real
power of PHP comes from its functions; it has more than 1000 built-in
functions.
PHP User
Defined Functions
Besides the
built-in PHP functions, we can create our own functions.
A function
is a block of statements that can be used repeatedly in a program.
A function
will not execute immediately when a page loads.
A function
will be executed by a call to the function.
Create a
User Defined Function in PHP
A user
defined function declaration starts with the word "function":
Syntax
function
functionName() {
code to be executed;
}
Note: A
function name can start with a letter or underscore (not a number).
Tip: Give
the function a name that reflects what the function does!
Function
names are NOT case-sensitive.
In the example
below, we create a function named "writeMsg()". The opening curly
brace ( { ) indicates the beginning of the function code and the closing curly
brace ( } ) indicates the end of the function. The function outputs "Hello
world!". To call the function, just write its name:
Example
<?php
function
writeMsg() {
echo "Hello world!";
}
writeMsg();
// call the function
?>
PHP Function
Arguments
Information
can be passed to functions through arguments. An argument is just like a
variable.
Arguments
are specified after the function name, inside the parentheses. You can add as
many arguments as you want, just separate them with a comma.
The
following example has a function with one argument ($fname). When the
familyName() function is called, we also pass along a name (e.g. Jani), and the
name is used inside the function, which outputs several different first names,
but an equal last name:
Example
<?php
function
familyName($fname) {
echo "$fname Refsnes.<br>";
}
familyName("Jani");
familyName("Hege");
familyName("Stale");
familyName("Kai
Jim");
familyName("Borge");
?>
The
following example has a function with two arguments ($fname and $year):
Example
<?php
function
familyName($fname, $year) {
echo "$fname Refsnes. Born in $year
<br>";
}
familyName("Hege",
"1975");
familyName("Stale",
"1978");
familyName("Kai
Jim", "1983");
?>
PHP Default
Argument Value
The
following example shows how to use a default parameter. If we call the function
setHeight() without arguments it takes the default value as argument:
Example
<?php
function
setHeight($minheight = 50) {
echo "The height is : $minheight
<br>";
}
setHeight(350);
setHeight();
// will use the default value of 50
setHeight(135);
setHeight(80);
?>
PHP
Functions - Returning values
To let a
function return a value, use the return statement:
Example
<?php
function
sum($x, $y) {
$z = $x + $y;
return $z;
}
echo
"5 + 10 = " . sum(5, 10) . "<br>";
echo
"7 + 13 = " . sum(7, 13) . "<br>";
echo
"2 + 4 = " . sum(2, 4);
?>
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