If statement execution flow in PHP

Introduction

An if statement helps your program decide what to do based on a condition. It lets your code choose between different paths.

When you want to check if a user is logged in before showing a page.

When you want to give a discount only if the purchase amount is over a certain value.

When you want to show a message if a form field is empty.

When you want to run different code depending on the time of day.

Syntax

PHP

<?php
if (condition) {
    // code to run if condition is true
} elseif (another_condition) {
    // code to run if the first condition is false and this one is true
} else {
    // code to run if all above conditions are false
}
?>

The condition is a statement that is either true or false.

The elseif and else parts are optional.

Examples

This checks if age is 18 or more, then prints a message.

PHP

<?php
if ($age >= 18) {
    echo "You can vote.";
}
?>

This chooses a grade based on the score using if, elseif, and else.

PHP

<?php
if ($score >= 90) {
    echo "Grade A";
} elseif ($score >= 80) {
    echo "Grade B";
} else {
    echo "Grade C or below";
}
?>

Sample Program

This program checks the temperature and prints a message based on its value.

PHP

<?php
$temperature = 25;
if ($temperature > 30) {
    echo "It's hot outside.";
} elseif ($temperature >= 20) {
    echo "The weather is nice.";
} else {
    echo "It's cold outside.";
}
?>

Important Notes

Only one block of code inside the if-elseif-else runs, the first true condition found.

If no condition is true and there is no else, nothing happens.

Summary

If statements let your program choose what to do based on conditions.

Use elseif to check multiple conditions in order.

Use else to run code when no conditions are true.

Practice

1. What does an if statement do in PHP?

easy

A. It defines a function.

B. It repeats code multiple times.

C. It runs code only if a condition is true.

D. It stops the program immediately.

Solution

1. Step 1: Understand the purpose of an if statement

   An if statement checks a condition and runs code only if that condition is true.

2. Step 2: Compare with other options

   Repeating code is done by loops, functions define reusable code, and stopping the program is done by exit or die.

3. Final Answer:

   It runs code only if a condition is true. -> Option C

4. Quick Check:

   If statement = runs code if true [OK]

Hint: If checks condition; runs code only when true [OK]

Common Mistakes:

• Confusing if with loops
• Thinking if defines functions
• Believing if stops the program

2. Which of the following is the correct syntax for an if statement in PHP?

easy

A. if condition { echo 'Yes'; }

B. if (condition) { echo 'Yes'; }

C. if condition: echo 'Yes'; endif;

D. if [condition] { echo 'Yes'; }

Solution

1. Step 1: Recall PHP if statement syntax

   In PHP, the condition must be inside parentheses and the code block inside curly braces.

2. Step 2: Check each option

   if (condition) { echo 'Yes'; } matches the correct syntax: if (condition) { ... }. if condition { echo 'Yes'; } misses parentheses, C uses alternate syntax but missing parentheses, D uses square brackets which is invalid.

3. Final Answer:

   if (condition) { echo 'Yes'; } -> Option B

4. Quick Check:

   Parentheses around condition = correct syntax [OK]

Hint: Always use parentheses around condition in if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Using square brackets instead of parentheses
• Confusing alternate syntax without proper format

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

$x = 10;
if ($x > 10) {
  echo 'Greater';
} elseif ($x == 10) {
  echo 'Equal';
} else {
  echo 'Less';
}

medium

A. Equal

B. No output

C. Less

D. Greater

Solution

1. Step 1: Evaluate the condition $x > 10

   $x is 10, so $x > 10 is false. The first if block is skipped.

2. Step 2: Check the elseif condition $x == 10

   This condition is true, so it prints 'Equal' and skips the else block.

3. Final Answer:

   Equal -> Option A

4. Quick Check:

   10 == 10 prints Equal [OK]

Hint: Check conditions top to bottom; first true runs [OK]

Common Mistakes:

• Assuming > includes equal
• Ignoring elseif and jumping to else
• Thinking multiple blocks run

4. Find the error in this PHP code:

if $a > 5 {
  echo 'Big';
} else {
  echo 'Small';
}

medium

A. Wrong keyword else

B. Missing semicolon after echo

C. Curly braces not allowed

D. Missing parentheses around condition

Solution

1. Step 1: Check if statement syntax

   In PHP, the condition must be inside parentheses. Here, if $a > 5 is missing parentheses.

2. Step 2: Verify other parts

   Semicolons after echo statements are optional if echo is used as a statement, else keyword is correct, and curly braces are allowed.

3. Final Answer:

   Missing parentheses around condition -> Option D

4. Quick Check:

   Condition must be in parentheses [OK]

Hint: Always put condition inside parentheses in if [OK]

Common Mistakes:

• Forgetting parentheses around condition
• Thinking else keyword is wrong
• Believing semicolon is mandatory after echo

5. Given this PHP code, what will be the output?

$score = 75;
if ($score >= 90) {
  echo 'A';
} elseif ($score >= 80) {
  echo 'B';
} elseif ($score >= 70) {
  echo 'C';
} else {
  echo 'F';
}

hard

A. C

B. A

C. B

D. F

Solution

1. Step 1: Check first condition $score >= 90

   75 is less than 90, so this is false. Skip to next.

2. Step 2: Check second condition $score >= 80

   75 is less than 80, so false again. Skip to next.

3. Step 3: Check third condition $score >= 70

   75 is greater than or equal to 70, so true. It prints 'C' and skips else.

4. Final Answer:

   C -> Option A

5. Quick Check:

   75 >= 70 prints C [OK]

Hint: Check conditions top-down; first true runs [OK]

Common Mistakes:

• Choosing wrong grade for score
• Ignoring elseif order
• Assuming else runs always