Follow this lesson in Ullman Chapter 10. The scripts are located in the 10 directory.
function function_name () {
#do stuff here
}Function names are case-insensitive!
For example:
<?php
function my_first_function() {
for($i = 0; $i < 10; $i++) {
echo “This is iteration $i. <br />”;
}
}echo “Here’s where we call my_first_function: <br />”;
my_first_function();
echo “The function has completed.”;
?>
if (function_exists(‘my_first_function’)) {
….
}
function function_name (argument1, argument2, …) {
#do stuff here
}For example:
<?php
function my_arguments_function($user_name, $user_title) {
echo “Hi, $user_name.<br />”;
echo “You are a(n) $user_title.<br />”;
}echo “Here’s where we call my_arguments_function: <br />”;
my_arguments_function(‘Fred’, ‘Antihero’);
echo “The function has completed.”;
?>
<?php
// Notice that if no message is passed,
// “Hi there” is used by default:
function my_defaults_function ($count, $msg = “Hi there.”) {
for($i = 0; $i < $count; $i++){
echo “Saying: $msg for repetition: $i .”<br />”;
}
}
echo “Print it 3 times ….<br />”;
my_defaults_function (3, “Hello”);
?>Default argument values, if there are any, must be named last! This has the benefit of making them optional.
Use the return statement:
function function_name ($arg1) {
statements();
return $value;
}For instance:
function my_calculator ($quantity, $price) {
// Calculate:
$total = $quantity * $price;
// Format:
$total = number_format ($total, 2);// Return the value:
return $total;}
Then use it like this:
$sale_total = my_calculator ($order_qty, $sale_price);
A variable you declare within a function is local to that function. It isn’t available elsewhere.
Variables declared using global are exactly that: available globally, both within and outside of particular functions.
Environment variables (like $_SERVER[‘PHP_SELF’]) are available not just to your PHP environment, but to everyone’s.
To use a global variable, declare it early in your script, outside any function:
$tax_rate = 6.875;
Then you can make this declaration within a function:
global $tax_rate;
Your script will use the external (global) variable, as long as it exists outside the function.
Review Chapter 10 of Ullman.