Static properties and methods in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing static property inside class

What is the output of this PHP code?

PHP

<?php
class Counter {
    public static $count = 0;
    public static function increment() {
        self::$count++;
    }
}
Counter::increment();
Counter::increment();
echo Counter::$count;
?>

A 1

B 2

C 0

D Fatal error: Access to undeclared static property

💡 Hint

Static properties keep their value shared across all calls.

The static property $count starts at 0. Each call to increment() increases it by 1. After two calls, $count is 2.

❓ Predict Output

intermediate

Output of static method called from instance

What will this PHP code output?

PHP

<?php
class Logger {
    public static function log() {
        echo "Logging message";
    }
}
$log = new Logger();
$log->log();
?>

A Nothing, no output

B Fatal error: Cannot call static method from instance

C Logging message

D Warning: Static method called non-statically

💡 Hint

In PHP, static methods can be called from instances but it's not recommended.

PHP allows calling static methods from an instance, so it outputs the string.

🔧 Debug

advanced

Identify the error in static property access

What error will this PHP code produce?

PHP

<?php
class Sample {
    public static $value = 10;
    public function show() {
        echo $this->value;
    }
}
$obj = new Sample();
$obj->show();
?>

A Notice: Undefined property: Sample::$value

B 10

C Fatal error: Access to static property via non-static context

D Warning: Using $this to access static property

💡 Hint

Static properties must be accessed with self:: or ClassName:: inside methods.

Using $this->value tries to access an instance property, but $value is static, so PHP raises a notice about undefined property.

📝 Syntax

advanced

Which option correctly defines and accesses a static property?

Which of the following PHP code snippets will run without syntax errors and output 5?

A

<?php
class Test {
    public static $num = 5;
}
echo Test::$num;
?>

B

<?php
class Test {
    static $num = 5;
}
echo Test::$num;
?>

C

<?php
class Test {
    public static $num = 5
}
echo Test::$num;
?>

D

<?php
class Test {
    public static $num = 5;
}
echo Test->num;
?>

💡 Hint

Check for missing semicolons and correct static property access syntax.

Option A correctly declares a public static property with a semicolon and accesses it with ClassName::$property. Option A misses 'public' but is valid in PHP 7+, but to keep one correct answer, we choose A. Option A misses semicolon causing syntax error. Option A uses wrong access syntax.

🚀 Application

expert

How many times is the static property incremented?

Consider this PHP code. How many times will the static property $counter be incremented after running all lines?

PHP

<?php
class Incrementer {
    public static $counter = 0;
    public function add() {
        self::$counter++;
    }
}
$a = new Incrementer();
$b = new Incrementer();
$a->add();
$b->add();
Incrementer::add();
?>

A 2

B 3

C 1

D Fatal error: Cannot call non-static method statically

💡 Hint

Check if the method add() is declared static or not before calling it statically.

The method add() is not declared static, so calling Incrementer::add() causes a fatal error.