A static variable in PHP retains its value between function calls. Declared with the static keyword inside a function, it is initialized only once and preserves its state across subsequent calls. For example, a counter function using a static variable increments correctly each time it’s called, instead of resetting. Uses include caching results, counting invocations, and avoiding repeated expensive operations. However, they can complicate testing and debugging, do not persist across requests, and are shared across all function calls within the same request, so caution is needed in multi-user environments.
A static variable inside a PHP function is a variable that retains its value between multiple calls to that function. Unlike regular local variables, which are reinitialized every time the function runs, a static variable keeps its state.
This can be really handy when you want to preserve some data across function executions without using global variables or external storage.
How does a static variable work in PHP?
When you declare a variable as static inside a function, it's only initialized once — the first time the function is called. Any changes made to the variable during one call persist into the next.
Here’s a simple example:
function counter() {
static $count = 0;
echo $count . "\n";
$count ;
}If you call counter() multiple times like this:
counter(); // outputs 0 counter(); // outputs 1 counter(); // outputs 2
You’ll see that $count doesn’t reset each time — it remembers where it left off.
Why use static variables in functions?
There are a few practical uses for static variables:
- Caching results within a function that gets called multiple times.
- Counting how many times a function has been invoked.
- Avoiding repeated expensive operations, like opening a file or connecting to a database every time the function runs.
It’s not always necessary, but when you need something to "remember" past behavior without going full object-oriented, static variables can be useful.
What to watch out for
Static variables aren't all sunshine and rainbows. Here are a few gotchas:
- They can make your code harder to test or debug if their behavior isn’t clearly documented.
- Since they retain values per request, they won’t help with cross-request persistence (like storing user sessions).
- If you're working in a multi-user environment, remember that static variables are shared across all calls in the same request — so be careful with them in functions used by different parts of your app.
Also, don’t confuse static variables inside functions with static properties or methods in classes — they behave differently.
So yeah, static variables in PHP functions are basically a way to keep track of something between calls without resorting to globals or other tricks. It's not something you'll use every day, but when you need it, it just works.
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