Comparison operators (loose and strict) in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if two variables are equal using loose comparison.

PHP

<?php
$a = 5;
$b = '5';
if ($a [1] $b) {
    echo 'Equal';
} else {
    echo 'Not equal';
}
?>

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

A==

B===

C!=

D!==

Attempts:

3 left

💡 Hint

Common Mistakes

Using === instead of == causes the comparison to fail because types differ.

The == operator checks if two values are equal after type juggling (loose comparison).

2fill in blank

medium

Complete the code to check if two variables are equal using strict comparison.

PHP

<?php
$x = 10;
$y = '10';
if ($x [1] $y) {
    echo 'Strictly equal';
} else {
    echo 'Not strictly equal';
}
?>

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

A!==

B==

C!=

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using == instead of === causes the comparison to ignore type differences.

The === operator checks if two values are equal and of the same type (strict comparison).

3fill in blank

hard

Fix the error in the code to correctly check if two variables are not equal using strict comparison.

PHP

<?php
$a = 7;
$b = '7';
if ($a [1] $b) {
    echo 'Not strictly equal';
} else {
    echo 'Strictly equal';
}
?>

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

A!==

B==

C!=

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using != instead of !== causes type differences to be ignored.

The !== operator checks if two values are not equal or not of the same type (strict inequality).

4fill in blank

hard

Fill both blanks to create a dictionary (associative array) with keys as numbers and values as their strict equality check with 10.

PHP

<?php
$results = [
    8 => (8 [1] 10),
    10 => (10 [2] 10)
];
print_r($results);
?>

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

A===

B==

C!==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing == and === causes inconsistent results.

Using === checks strict equality for both keys with 10.

5fill in blank

hard

Fill all three blanks to create an array filtering numbers strictly greater than 5 and loosely equal to '7'.

PHP

<?php
$numbers = [3, 5, 7, '7', 10];
$filtered = array_filter($numbers, function($num) {
    return $num [1] 5 && $num [2] '7' && $num [3] 7;
});
print_r($filtered);
?>

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

A>

B==

C===

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < instead of > changes the filter logic.

Mixing up == and === causes unexpected results.

The code filters numbers greater than 5, loosely equal to '7', and strictly equal to 7.

Practice

1. Which PHP comparison operator checks both value and type strictly?

easy

A. ===

B. ==

C. !=

D. <>

Solution

1. Step 1: Understand loose vs strict comparison

   Loose comparison (==) checks value after type conversion, strict (===) checks value and type exactly.

2. Step 2: Identify operator that checks type and value

   The operator === compares both type and value strictly without conversion.

3. Final Answer:

   === -> Option A

4. Quick Check:

   Strict comparison = === [OK]

Hint: Use === to compare type and value exactly [OK]

Common Mistakes:

• Confusing == with ===
• Thinking != checks type
• Using <> instead of !=

2. Which of the following is the correct syntax for a strict inequality check in PHP?

easy

A. !=

B. !==

C. <>

D. !===

Solution

1. Step 1: Recall PHP strict inequality operator

   Strict inequality operator in PHP is !== which checks both type and value are not equal.

2. Step 2: Identify correct syntax

   !== is valid syntax; !=== is invalid and others are loose inequality.

3. Final Answer:

   !== -> Option B

4. Quick Check:

   Strict inequality = !== [OK]

Hint: Use !== for strict not equal check [OK]

Common Mistakes:

• Using !=== which is invalid
• Confusing != with !==
• Using <> for strict inequality

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

$a = 0;
$b = '0';
var_dump($a == $b);
var_dump($a === $b);

medium

A. bool(true) bool(false)

B. bool(false) bool(true)

C. bool(true) bool(true)

D. bool(false) bool(false)

Solution

1. Step 1: Evaluate loose comparison ($a == $b)

   0 (int) and '0' (string) are equal after type conversion, so $a == $b is true.

2. Step 2: Evaluate strict comparison ($a === $b)

   Types differ (int vs string), so $a === $b is false.

3. Final Answer:

   bool(true) bool(false) -> Option A

4. Quick Check:

   Loose == true, Strict === false [OK]

Hint: Remember === checks type too, == converts types [OK]

Common Mistakes:

• Assuming both comparisons return true
• Ignoring type difference in strict check
• Confusing output order

4. Find the error in this PHP code snippet:

$x = 5;
if ($x = '5') {
  echo 'Equal';
} else {
  echo 'Not equal';
}

medium

A. Missing semicolon after echo

B. Using strict comparison (===) instead of loose

C. Assignment (=) used instead of comparison (==)

D. Variable $x is not defined

Solution

1. Step 1: Identify operator in if condition

   The condition uses = which assigns '5' to $x instead of comparing.

2. Step 2: Understand effect of assignment in condition

   Assignment returns the assigned value, which is truthy, so 'Equal' always prints regardless of original $x.

3. Final Answer:

   Assignment (=) used instead of comparison (==) -> Option C

4. Quick Check:

   Use == for comparison, not = [OK]

Hint: Use == for comparison, not = assignment [OK]

Common Mistakes:

• Confusing = with == in conditions
• Thinking strict comparison is error here
• Ignoring that assignment returns value

5. You want to filter an array to keep only elements that are exactly integer 0, excluding string '0'. Which comparison operator should you use in PHP?

hard

A. ==

B. !==

C. !=

D. ===

Solution

1. Step 1: Understand filtering requirement

   We want to keep only elements that are integer 0, not string '0'. So type matters.

2. Step 2: Choose operator that checks type and value

   Strict equality (===) checks both value and type, so it excludes string '0'.

3. Final Answer:

   === -> Option D

4. Quick Check:

   Strict equality === filters exact type and value [OK]

Hint: Use === to match exact type and value [OK]

Common Mistakes:

• Using == which allows type conversion
• Using != or !== which exclude 0
• Ignoring type difference in filtering