5.5. Using Static Variables
Problem
You want a local variable to retain its value between invocations of a function.
Solution
Declare the variable as static
:
function track_times_called( ) { static $i = 0; $i++; return $i; }
Discussion
Declaring a variable
static
causes its value to be remembered by a
function. So, if there are subsequent calls to the function, you can
access the value of the saved variable. The
pc_check_the_count( )
function shown in Example 5-1 uses static
variables to
keep track of the strikes and balls for a baseball batter.
Example 5-1. pc_check_the_count( )
function pc_check_the_count($pitch) { static $strikes = 0; static $balls = 0; switch ($pitch) { case 'foul': if (2 == $strikes) break; // nothing happens if 2 strikes // otherwise, act like a strike case 'strike': $strikes++; break; case 'ball': $balls++; break; } if (3 == $strikes) { $strikes = $balls = 0; return 'strike out'; } if (4 == $balls) { $strikes = $balls = 0; return 'walk'; } return 'at bat'; } $what_happened = check_the_count($pitch);
In pc_check_the_count( )
, the logic of what
happens to the batter depending on the pitch count is in the
switch
statement inside the function. You can
instead return the number of strikes and balls, but this requires you
to place the checks for striking out, walking, and staying at the
plate in multiple places in the code.
While static
variables retain their values between
function calls, they do so only during one invocation of a script. A
static
variable accessed ...
Get PHP Cookbook now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.