PHP: Function Assignment parameter default initial value

Default parameters for functions

When you are allowed to define a function, specify the default value for the parameter, such as:

function Js_location ($url, $alert = ', $top = ') {
if ($alert = = "&& $top = =") {
Header ("Location: $url");
Exit
}

Echo ' <script language= ' JavaScript > ';
if ($alert) {
echo ' Alert ('. Js_contents_code ($alert). ' \‘);‘;
}
echo "window{$top}.location= ' $url ';";
Echo ' </script> ';
Exit
}

At this point, the js_location function parameter $alert, $top specify the default value, you can not pass, but the URL must be passed. Many of the previous parameters of a system function are mandatory, followed by an option, defined in such a way as the test function, such as printf (), mysql_query (), and so on.

PHP: Function Assignment parameter default initial value