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PHP 5 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.
on will be executed by a call to the function.
Syntax

function yourfunctionName() {
code to be executed;
}

Note*: A function name can start with a letter or underscore (not a number).
In the example below, we create a function named "abc()". 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:

<?php
function abc() {
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 seperate them with a comma.
The following example has a function with one argument ($fname). When the Name() 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:

<?php
function Name($fname) {
echo "$fname Refsnes.<br>";
}

familyName("Jani");
familyName("Heges");
familyName("Stales");
familyName("Kai Jims");
familyName("Borges");
?>
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:

<?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:

<?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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