Question

On my website there is a php function func1(), which gets some info from other resources. It is very costly to run this function.

I want that when Visitor1 comes to my website then this func1() is executed and the value is stored in $variable1=func1(); in a text file (or something, but not a database).

Then a time interval of 5 min starts and when during this interval Visitor2 visits my website then he gets the value from the text file without calling the function func1().

When Visitor3 comes in 20 min, the function should be used again and store the new value for 5 minutes.

How to make it? A small working example would be nice.

Answer 1

Store it in a file, and check the file’s timestamp with filemtime(). If it’s too old, refresh it.

$maxage = 1200; // 20 minutes...
// If the file already exists and is older than the max age
// or doesn't exist yet...
if (!file_exists("file.txt") || (file_exists("file.txt") && filemtime("file.txt") < (time() - $maxage))) {
  // Write a new value with file_put_contents()
  $value = func1();
  file_put_contents("file.txt", $value);
}
else {
  // Otherwise read the value from the file...
  $value = file_get_contents("file.txt");
}

Note: There are dedicated caching systems out there already, but if you only have this one value to worry about, this is a simple caching method.