Normally, when a function is completed/executed, all of its variables are deleted. However, sometimes we want a local variable NOT to be deleted. We need it for a further job. To do this, use the static keyword when you first declare the variable:

<?php
function myTest() {
  static $x = 0;
  echo $x;
  $x++;
}

myTest(); // output  is 1
myTest(); // output  is 2
myTest(); // output is 3
?>

Then, each time the function is called, that variable will still have the information it contained from the last time the function was called. Note: The variable is still local to the function.