Static properties and methods in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the static property inside the class.

PHP

<?php
class Counter {
    public static $count = 0;
    public static function increment() {
        self::[1]++;
    }
}
Counter::increment();
echo Counter::$count;

Drag options to blanks, or click blank then click option'

Athis->count

Bself::$count

Ccount

D$count

Attempts:

3 left

💡 Hint

Common Mistakes

Using count (without $) after self:: treats it as a constant, causing an error.

Using this->count inside static method is invalid.

Inside the class, static properties are accessed with self::$propertyName. The blank completes self::$count++.

2fill in blank

medium

Complete the code to call the static method from outside the class.

PHP

<?php
class Logger {
    public static function log($msg) {
        echo $msg;
    }
}
Logger::[1]('Hello World');

Drag options to blanks, or click blank then click option'

Alog

Bwrite

Cecho

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using print or echo as method names causes errors.

Trying to call method with -> instead of ::.

Static methods are called using ClassName::methodName(). Here, the method is named log, so Logger::log('Hello World') is correct.

3fill in blank

hard

Fix the error in accessing the static property inside the static method.

PHP

<?php
class User {
    public static $count = 0;
    public static function addUser() {
        [1]++;
    }
}
User::addUser();
echo User::$count;

Drag options to blanks, or click blank then click option'

Aself::$count

B$count

Cthis->count

DUser->count

Attempts:

3 left

💡 Hint

Common Mistakes

Using $count without self:: causes undefined variable error.

Using this->count inside static method causes error.

Inside static methods, static properties must be accessed with self::$propertyName. Using $count or this->count causes errors.

4fill in blank

hard

Fill both blanks to create a static method that returns the static property value.

PHP

<?php
class Config {
    public static $version = '1.0';
    public static function getVersion() {
        return [1]::[2];
    }
}
echo Config::getVersion();

Drag options to blanks, or click blank then click option'

Aself

BConfig

C$version

Dversion

Attempts:

3 left

💡 Hint

Common Mistakes

Using version (without $) after :: treats it as a constant, causing an error.

Using Config::version inside method is allowed but self::$version is preferred.

Inside the class, use self:: to refer to the class itself, and static properties are accessed with self::$propertyName, so self::$version.

5fill in blank

hard

Fill all three blanks to define and use a static property and method that increments and returns the count.

PHP

<?php
class Visitor {
    public static [1] = 0;
    public static function [2]() {
        self::[1]++;
        return self::[1];
    }
}
echo Visitor::[2]();

Drag options to blanks, or click blank then click option'

A$count

Bincrement

Ccount

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using count (without $) in declaration or after self:: causes syntax or constant errors.

Using wrong method name causes call errors.

Static property is declared as public static $count = 0;, so BLANK_1 is '$count'. Static method is increment. Inside method self::$count is used.

Practice

1. Which statement about static properties in PHP is true?
class Example { public static $count = 0; }

easy

A. Static properties belong to the class itself, not to any object instance.

B. Static properties can only be accessed through object instances.

C. Static properties cannot hold values.

D. Static properties are private by default.

Solution

1. Step 1: Understand static property ownership

   Static properties belong to the class, not to individual objects.

2. Step 2: Check access rules

   Static properties are accessed using the class name, not object instances.

3. Final Answer:

   Static properties belong to the class itself, not to any object instance. -> Option A

4. Quick Check:

   Static property = class-level data [OK]

Hint: Static means class-level, not per object [OK]

Common Mistakes:

• Thinking static properties belong to objects
• Trying to access static properties via objects
• Assuming static properties can't hold values

2. Which of the following is the correct syntax to call a static method show() of class Test?

easy

A. $obj->show();

B. $obj::show();

C. Test->show();

D. Test::show();

Solution

1. Step 1: Recall static method call syntax

   Static methods are called using the class name and double colon (::).

2. Step 2: Check each option

   Test::show(); uses Test::show(); which is correct syntax.

3. Final Answer:

   Test::show(); -> Option D

4. Quick Check:

   Static method call = ClassName::method() [OK]

Hint: Use ClassName::method() to call static methods [OK]

Common Mistakes:

• Using object arrow (->) to call static methods
• Using object variable with :: operator incorrectly
• Using class arrow (->) which is invalid

3. What will be the output of the following PHP code?

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

medium

A. 1

B. 2

C. 0

D. Error

Solution

1. Step 1: Understand static property and method behavior

   Static property $count starts at 0 and is shared by the class.

2. Step 2: Trace method calls

   Each call to increment() increases $count by 1. Two calls increase it to 2.

3. Final Answer:

   2 -> Option B

4. Quick Check:

   2 increments = 2 count [OK]

Hint: Static property keeps value across calls [OK]

Common Mistakes:

• Thinking static resets per call
• Confusing self:: with $this->
• Expecting error due to static usage

4. Identify the error in this PHP code snippet:

class Sample {
    public static $value = 10;
    public function show() {
        echo self->$value;
    }
}
$object = new Sample();
$object->show();

medium

A. Cannot use echo inside class methods.

B. Static property cannot be accessed inside non-static methods.

C. Using self::$value instead of self->$value inside the method.

D. Missing static keyword before method declaration.

Solution

1. Step 1: Check static property access syntax

   Static properties must be accessed with self::$propertyName, not self->$propertyName.

2. Step 2: Verify method and property usage

   The method is non-static but can access static properties using self:: syntax.

3. Final Answer:

   Using self::$value instead of self->$value inside the method. -> Option C

4. Quick Check:

   Static property access = self::$property [OK]

Hint: Use :: for static properties, not -> or $ [OK]

Common Mistakes:

• Using $ before property name with self::
• Trying to access static property with $this->
• Confusing static and non-static method rules

5. You want to count how many objects of class User have been created using a static property. Which code correctly implements this?

class User {
    public static $count = 0;
    public function __construct() {
        // What goes here?
    }
}

hard

A. self::$count++;

B. $this->count++;

C. User->count++;

D. static->count++;

Solution

1. Step 1: Understand static property increment in constructor

   Each time an object is created, the constructor runs and should increase the static count.

2. Step 2: Use correct syntax to increment static property

   Use self::$count++; inside the constructor to increment the static property.

3. Final Answer:

   self::$count++; -> Option A

4. Quick Check:

   Increment static with self::$property++ [OK]

Hint: Use self::$property to access static inside class [OK]

Common Mistakes:

• Using $this->count++ which accesses instance property
• Using arrow (->) with class name or static keyword
• Trying to increment static property without self::