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