Comparison operators (loose and strict) in PHP - Mini Project: Build & Apply

Comparison operators (loose and strict)

📖 Scenario: You are working on a simple PHP script that compares values to check if they are equal or identical. This is useful when you want to understand how PHP treats different types of comparisons.

🎯 Goal: Build a PHP script that demonstrates the difference between loose equality (==) and strict equality (===) operators by comparing different values.

📋 What You'll Learn

Create variables with specific values

Create a variable to hold a comparison result

Use both loose and strict comparison operators

Print the comparison results

💡 Why This Matters

🌍 Real World

Understanding how PHP compares values helps avoid bugs when checking user input, form data, or database values.

💼 Career

Many PHP jobs require careful handling of data types and comparisons to ensure correct program logic and security.

1

Create variables with specific values

Create two variables called $a and $b. Set $a to the integer 5 and $b to the string '5'.

PHP

<?php

// Create variables $a and $b with values 5 and '5'
// Your code here

Hint

Use $a = 5; and $b = '5'; to create the variables.

2

Create a variable to hold a comparison result

Create a variable called $looseEqual and set it to the result of comparing $a and $b using the loose equality operator ==.

PHP

<?php
$a = 5;
$b = '5';

// Create $looseEqual to store result of $a == $b
// Your code here

Hint

Use $looseEqual = ($a == $b); to compare loosely.

3

Use strict equality operator for comparison

Create a variable called $strictEqual and set it to the result of comparing $a and $b using the strict equality operator ===.

PHP

<?php
$a = 5;
$b = '5';
$looseEqual = ($a == $b);

// Create $strictEqual to store result of $a === $b
// Your code here

Hint

Use $strictEqual = ($a === $b); to compare strictly.

4

Print the comparison results

Print the values of $looseEqual and $strictEqual using var_dump() to show the comparison results.

PHP

<?php
$a = 5;
$b = '5';
$looseEqual = ($a == $b);
$strictEqual = ($a === $b);

// Print $looseEqual and $strictEqual using var_dump()
// Your code here

Hint

Use var_dump($looseEqual); and var_dump($strictEqual); to print the results.

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