Ternary operator in PHP - Step-by-Step Execution

Concept Flow - Ternary operator

Evaluate condition

Yes↓

Use value if true

↓

Result

No↓

Use value if false

↓

Result

The ternary operator checks a condition and returns one value if true, another if false.

Execution Sample

PHP

<?php
$age = 20;
$status = ($age >= 18) ? 'Adult' : 'Minor';
echo $status;
?>

This code checks if age is 18 or more, then sets status to 'Adult' or 'Minor' accordingly.

Execution Table

Step	Condition	Condition Result	Value if True	Value if False	Result assigned to $status
1	$age >= 18	20 >= 18 is True	'Adult'	'Minor'	'Adult'
2	End of expression	-	-	-	Execution stops

💡 Condition is true, so 'Adult' is assigned to $status and execution ends.

Variable Tracker

Variable	Start	After Step 1	Final
$age	20	20	20
$status	undefined	'Adult'	'Adult'

Key Moments - 2 Insights

Why does $status get 'Adult' and not 'Minor'?

Because the condition $age >= 18 is true at step 1 in the execution_table, so the true value 'Adult' is chosen.

What if $age was 16? What would happen?

If $age was 16, the condition would be false, so the false value 'Minor' would be assigned to $status instead.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $status after step 1?

A 20

B 'Minor'

C 'Adult'

D undefined

💡 Hint

Check the 'Result assigned to $status' column in row 1 of execution_table.

At which step does the ternary operator decide the value of $status?

A Step 2

B Step 1

C Before Step 1

D After Step 2

💡 Hint

Look at the 'Condition Result' and 'Result assigned to $status' columns in execution_table.

If $age was 15, what would be the result assigned to $status?

A 'Minor'

B 15

C 'Adult'

D undefined

💡 Hint

Think about the condition $age >= 18 and what happens if it is false.

Concept Snapshot

Ternary operator syntax: (condition) ? value_if_true : value_if_false;
It evaluates the condition once.
Returns value_if_true if condition is true.
Returns value_if_false if condition is false.
Useful for simple if-else in one line.

Full Transcript

The ternary operator in PHP is a shortcut for if-else. It checks a condition and returns one value if true, another if false. In the example, we check if $age is 18 or more. Since $age is 20, the condition is true, so $status is set to 'Adult'. If $age was less than 18, $status would be 'Minor'. This operator helps write simple decisions in one line.

Practice

1. What does the ternary operator condition ? value_if_true : value_if_false do in PHP?

easy

A. It chooses one of two values based on the condition's truth.

B. It creates a loop that runs twice.

C. It defines a function with two parameters.

D. It comments out a line of code.

Solution

1. Step 1: Understand the ternary operator format

   The ternary operator uses a condition followed by a question mark, then two values separated by a colon.

2. Step 2: Identify its purpose

   It returns the first value if the condition is true, otherwise the second value.

3. Final Answer:

   It chooses one of two values based on the condition's truth. -> Option A

4. Quick Check:

   condition ? true_value : false_value = chooses value [OK]

Hint: Think: condition true? pick first : else pick second [OK]

Common Mistakes:

• Confusing ternary with loops
• Thinking it defines functions
• Assuming it comments code

2. Which of the following is the correct syntax for a ternary operator in PHP?

easy

A. condition ? value_if_true, value_if_false;

B. condition : value_if_true ? value_if_false;

C. condition ? value_if_true : value_if_false;

D. condition ? (value_if_true : value_if_false);

Solution

1. Step 1: Recall ternary operator syntax

   The correct syntax is: condition ? value_if_true : value_if_false;

2. Step 2: Check each option

   Only condition ? value_if_true : value_if_false; matches the correct syntax exactly.

3. Final Answer:

   condition ? value_if_true : value_if_false; -> Option C

4. Quick Check:

   Syntax = condition ? true : false [OK]

Hint: Remember: question mark before colon in ternary [OK]

Common Mistakes:

• Swapping question mark and colon
• Using comma instead of colon
• Adding extra parentheses incorrectly

3. What is the output of this PHP code?

$age = 20;
$result = ($age >= 18) ? 'Adult' : 'Minor';
echo $result;

medium

A. Adult

B. Error

C. 20

D. Minor

Solution

1. Step 1: Evaluate the condition

   $age is 20, so ($age >= 18) is true.

2. Step 2: Apply ternary operator

   Since condition is true, $result is set to 'Adult'.

3. Final Answer:

   Adult -> Option A

4. Quick Check:

   20 >= 18 ? 'Adult' : 'Minor' = 'Adult' [OK]

Hint: Check condition result true or false to pick output [OK]

Common Mistakes:

• Assuming output is the number 20
• Confusing true and false branches
• Expecting syntax error

4. Find the error in this PHP code using ternary operator:

$score = 75;
$grade = $score > 60 ? 'Pass' 'Fail';
echo $grade;

medium

A. Wrong variable name used

B. Missing colon ':' between true and false values

C. Ternary operator cannot be used with strings

D. Missing semicolon after echo

Solution

1. Step 1: Check ternary operator syntax

   The ternary operator requires a colon ':' between the true and false values.

2. Step 2: Identify the missing colon

   Code has 'Pass' 'Fail' without ':' causing syntax error.

3. Final Answer:

   Missing colon ':' between true and false values -> Option B

4. Quick Check:

   Syntax needs ? true : false [OK]

Hint: Always put ':' between true and false parts [OK]

Common Mistakes:

• Omitting colon ':'
• Using comma instead of colon
• Confusing variable names

5. Given an array of numbers, which PHP code correctly uses the ternary operator to create a new array labeling each number as 'Even' or 'Odd'?

hard

A. $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 == 1 ? 'Even' : 'Odd', $numbers);

B. $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 == 0 ? 'Odd' : 'Even', $numbers);

C. $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 ? 'Even' : 'Odd', $numbers);

D. $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 == 0 ? 'Even' : 'Odd', $numbers);

Solution

1. Step 1: Understand the condition for even or odd

   A number is even if $n % 2 == 0, otherwise odd.

2. Step 2: Check each option's condition and labels

   $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 == 0 ? 'Even' : 'Odd', $numbers); correctly labels even numbers as 'Even' and odd as 'Odd'. Others swap or invert labels.

3. Final Answer:

   $numbers = [1,2,3]; $labels = array_map(fn($n) => $n % 2 == 0 ? 'Even' : 'Odd', $numbers); -> Option D

4. Quick Check:

   Even check with ternary = correct labeling [OK]

Hint: Even numbers have remainder 0 when divided by 2 [OK]

Common Mistakes:

• Swapping 'Even' and 'Odd' labels
• Using wrong modulo condition
• Confusing truthy/falsy values in ternary