php-static variables

A static variable retains its value between calls to a function but is visible only within that function.
IT declare a variable static with the static keyword.

function test_counter (  ) {
  static $counter = 0;
  $counter++;
  echo "Static counter is now $counter\n";
}
$counter = 5;
test_counter(  );
test_counter(  );
echo "Global counter is $counter\n";
Static counter is now 1
Static counter is now 2
Global counter is 5

Variables declared outside a function are global.

 That is, they can be accessed from any part of the script. By default, 

they are not available inside functions.