Saving State Between Function Calls with the static Statement

Local variables within functions have a short but happy life they come into being when the function is called and die when execution is finished, as they should. Occasionally, however, you may want to give a function a rudimentary memory.
Let's assume that we want a function to keep track of the number of times it has been called so that numbered headings can be created by a script. We could, of course, use the global statement to do this, as shown in Listing below:
$num_of_calls = 0;
function numberedHeading($txt) {
global $num_of_calls;
echo "<h1>".$num_of_calls." ".$txt."</h1>";
numberedHeading("Mobile Phones");
echo "<p>We build a fine range of mobile phones.</p>";
echo "<p>Also Digital Cameras.</p>";

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