Function scope

Learn that variables inside a function are not visible outside.

Function scope

Variables defined inside a function are called local variables and are not visible from outside. So after function counter() { $n = 5; }, writing echo $n; outside raises an error in PHP.

This behavior is known as scope. Each function has its own scope; outer variables do not appear inside automatically. This keeps functions from mixing up each other's variables.

The global keyword

To use an outer variable inside a function, you can import it with the global keyword. Example: $score = 0; function addPoint() { global $score; $score += 1; }.

Using global does not copy the variable; the inside and outside share the same one. Still, many globals make code hard to follow; use them carefully.

Exercise Print a counter with a local variable

Define a parameterless function named showCounter. In the body, define $count = 1; and print it with echo $count . "\n";. Then call the function.

Show example solution

Write function showCounter() { $count = 1; echo $count . "\n"; }, then call with showCounter();.
Example solution:
<?php
// Define showCounter with a $count variable inside
function showCounter() {
    $count = 1;
    echo $count . "\n";
}
showCounter();

Test yourself

What does the code below do?
```
function show() {
    $city = "Ankara";
}
show();
echo $city;
```
- Prints Ankara
- Prints show
- Prints a blank line
- Errors, $city is undefined
Show answer

Errors, $city is undefined — Correct. $city is local to the function; it is undefined outside.

Complete the global declaration

$price = 100;

function showPrice() {
    ____ $price;
    echo $price;
}
showPrice();

Show answer

$price = 100;

function showPrice() {
    global $price;
    echo $price;
}
showPrice();

Match scope concepts

Defined inside function

Local variable
global $n

Reaches outer variable
Function without return

Returns null

Next lesson: Returning arrays from functions

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