You want to pass a variable to a function and have it retain any changes made to its value inside the function. To instruct a function to accept an argument passed by reference instead of value, prepend an & to the argument name. You can think of a reference as a signpost that points to a variable. In working with the reference, you are manipulating the value to which it points.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="EN" lang="EN">
<head>
<title>PHP</title>
<meta Name="Author" Content="Hann So">
</head>
<body>
<p>
<?php
function Add(&$num1, $num2 = "3")
{
echo "$num1 + $num2 = ", $num1+$num2, "<br />";
}
$val = 2;
Add($val);
function display_bold(&$string, $tag = 'b')
{
$string = "<$tag>$string</$tag>";
}
$string="Hello World";
display_bold($string);
echo $string;
?>
</p>
</body>
</html>
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