Comparison operators (loose and strict) in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of loose equality with different types

What is the output of this PHP code?

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

PHP

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

A string(1) "0"

B bool(false)

C int(0)

D bool(true)

💡 Hint

Loose equality compares values after type juggling.

The loose equality operator (==) converts types if needed. Here, integer 0 and string '0' are considered equal, so var_dump outputs bool(true).

❓ Predict Output

intermediate

Output of strict equality with different types

What is the output of this PHP code?

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

PHP

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

A bool(true)

B bool(false)

C int(0)

D string(1) "0"

💡 Hint

Strict equality checks both value and type.

The strict equality operator (===) requires both value and type to be the same. Here, integer 0 and string '0' differ in type, so var_dump outputs bool(false).

❓ Predict Output

advanced

Result of comparing null and empty string with loose equality

What is the output of this PHP code?

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

PHP

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

A bool(false)

B NULL

C bool(true)

D string(0) ""

💡 Hint

Loose equality considers null equal to empty string.

In PHP, null and empty string are NOT equal with loose equality (==). So var_dump outputs bool(false).

❓ Predict Output

advanced

Output of comparing boolean false and string '0' with loose equality

What is the output of this PHP code?

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

PHP

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

A bool(false)

B int(0)

C bool(true)

D string(1) "0"

💡 Hint

Loose equality converts both to boolean for comparison.

When comparing false and '0' with loose equality, PHP converts '0' to false, so they are equal and var_dump outputs bool(true).

❓ Predict Output

expert

Output of comparing array and string with loose equality

What is the output of this PHP code?

$a = [];
$b = '';
var_dump($a == $b);

PHP

$a = [];
$b = '';
var_dump($a == $b);

A bool(false)

B bool(true)

C array(0) {}

D string(0) ""

💡 Hint

Empty arrays and empty strings are equal with loose equality.

In PHP, an empty array and an empty string are NOT equal with loose equality (==). So var_dump outputs bool(false).

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