Variable naming rules in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable named $name with the value "John".

PHP

<?php
$[1] = "John";
?>

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

Aname!

B1name

Cmy-name

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Starting variable names with a number.

Using special characters like hyphens or exclamation marks in variable names.

In PHP, variable names must start with a letter or underscore and can contain letters, numbers, and underscores. $name is valid.

2fill in blank

medium

Complete the code to declare a variable named $user_age and assign it the value 30.

PHP

<?php
$[1] = 30;
?>

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

Auser_age

Buser-age

Cuser age

Duser.age

Attempts:

3 left

💡 Hint

Common Mistakes

Using hyphens or dots in variable names.

Including spaces in variable names.

Underscores are allowed in PHP variable names, so $user_age is valid.

3fill in blank

hard

Fix the error in the variable declaration to make it valid.

PHP

<?php
$[1] = "Hello";
?>

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

A_greeting

B2greeting

Cgreeting!

Dgreeting message

Attempts:

3 left

💡 Hint

Common Mistakes

Starting variable names with numbers.

Using spaces or special characters in variable names.

Variable names can start with an underscore and contain letters and numbers, so $_greeting is valid.

4fill in blank

hard

Fill both blanks to declare a variable named $totalCount and assign it the value 100.

PHP

<?php
$[1] = [2];
?>

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

AtotalCount

B100

Cone_hundred

DcountTotal

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid variable names with spaces or special characters.

Assigning numbers as strings when an integer is expected.

The variable name $totalCount is valid and assigning the integer 100 is correct.

5fill in blank

hard

Fill all three blanks to create an associative array with variable $person having keys name and age.

PHP

<?php
$[1] = [
    '[2]' => 'Alice',
    '[3]' => 25
];
?>

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

Aperson

Bname

Cage

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid variable names.

Using keys with spaces or special characters.

The variable $person holds an associative array with keys name and age, which are valid string keys.

Practice

1. Which of the following is a valid variable name in PHP?

easy

A. $user_name

B. 2ndUser

C. user-name

D. user name

Solution

1. Step 1: Check the first character of each variable

   PHP variables must start with a $ followed by a letter or underscore, not a number or space.

2. Step 2: Validate allowed characters

   Variable names can only contain letters, numbers, and underscores after the $. Spaces and hyphens are not allowed.

3. Final Answer:

   $user_name -> Option A

4. Quick Check:

   Starts with $ and uses letters/underscore [OK]

Hint: Variable names start with $ and no spaces or hyphens [OK]

Common Mistakes:

• Starting variable with a number
• Using spaces or hyphens in variable names
• Omitting the $ sign at the start

2. Which of these variable declarations will cause a syntax error in PHP?

easy

A. $totalAmount = 100;

B. $_count = 5;

C. $9value = 10;

D. $userName = 'John';

Solution

1. Step 1: Identify the variable starting characters

   PHP variables must start with $ followed by a letter or underscore, not a number.

2. Step 2: Check each option

   Options B, C, and D start correctly. $9value = 10; starts with $9, which is invalid.

3. Final Answer:

   Syntax error due to starting with a number -> Option C

4. Quick Check:

   Variable cannot start with number [OK]

Hint: Variables cannot start with numbers, only letters or _ after $ [OK]

Common Mistakes:

• Starting variable names with digits
• Confusing variable names with constants
• Missing the $ sign

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

$Var = 10;
$var = 20;
echo $Var + $var;

medium

A. 20

B. 30

C. 10

D. Error

Solution

1. Step 1: Understand variable case sensitivity in PHP

   PHP variable names are case-sensitive, so $Var and $var are different variables.

2. Step 2: Calculate the sum of both variables

   $Var is 10 and $var is 20, so their sum is 30.

3. Final Answer:

   30 -> Option B

4. Quick Check:

   Case-sensitive variables sum correctly [OK]

Hint: PHP variables are case-sensitive; $Var and $var differ [OK]

Common Mistakes:

• Assuming variables with different cases are the same
• Expecting a syntax error due to case difference
• Ignoring case sensitivity in variable names

4. Identify the error in this PHP code:

$1stName = 'Alice';
$lastName = 'Smith';
echo $1stName . ' ' . $lastName;

medium

A. Variable names cannot contain uppercase letters

B. Missing semicolon after echo statement

C. Concatenation operator is incorrect

D. Variable names cannot start with a number

Solution

1. Step 1: Check variable naming rules

   Variable names cannot start with a number. $1stName starts with '1', which is invalid.

2. Step 2: Verify other parts of the code

   The concatenation operator . and semicolons are correct, and uppercase letters are allowed.

3. Final Answer:

   Variable names cannot start with a number -> Option D

4. Quick Check:

   Variable names must start with letter or _ [OK]

Hint: Variable names cannot start with digits, only letters or underscore [OK]

Common Mistakes:

• Thinking uppercase letters are invalid
• Confusing concatenation operator with plus sign
• Missing semicolons causing errors

5. You want to store a user's age in a variable. Which variable name follows PHP naming rules and is the clearest choice?

hard

A. $userAge

B. $user-age

C. $age user

D. $2age

Solution

1. Step 1: Check PHP variable naming rules

   Variable names must start with $ followed by a letter or underscore, and can contain letters, numbers, and underscores only.

2. Step 2: Evaluate clarity and correctness of options

   $userAge uses camelCase with allowed characters. Options A and B contain hyphens and spaces, which are invalid. $2age starts with a number, which is invalid.

3. Final Answer:

   $userAge -> Option A

4. Quick Check:

   Clear, valid variable name with letters and no invalid characters [OK]

Hint: Use letters and underscores, no spaces or hyphens, start with $ [OK]

Common Mistakes:

• Using spaces or hyphens in variable names
• Starting variable names with numbers
• Choosing unclear or confusing names