User-Defined Functions
User-defined functions provide a way to group together related statements into a cohesive block. For reusable code, a function saves duplicating statements and makes maintenance of the code easier. Consider an example of a simple user-developed function as shown in Example 2-3.
Example 2-3. A user-defined function to output bold text
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html401/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Simple Function Call</title>
</head>
<body bgcolor="#ffffff">
<?php
function bold($string)
{
print "<b>" . $string . "</b>";
}
// First example function call (with a static string)
print "this is not bold ";
bold("this is bold ");
print "this is again not bold ";
// Second example function call (with a variable)
$myString = "this is bold";
bold($myString);
?>
</body></html>The script defines the function bold( ),
which takes one parameter, $string,
and prints that string prefixed by a bold <b> tag and suffixed with a </b> tag. The parameter $string is a variable that is available in the
body of the function, and the value of $string is set when the function is called. As
shown in the example, the function can be called with a string literal
expression or a variable as the parameter.
Functions can also return values. For example, consider the following code fragment that declares and uses a function heading( ), which returns a string ...
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