Gettype and typeof checks in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the gettype() function do in PHP?

The gettype() function returns the type of a variable as a string, like 'integer', 'string', or 'array'.

beginner

Is there a typeof operator in PHP like in JavaScript?

No, PHP does not have a typeof operator. Instead, it uses functions like gettype() or is_*() functions to check types.

beginner

How can you check if a variable is an integer in PHP?

You can use is_int($var) which returns true if $var is an integer.

beginner

What type string does gettype() return for a boolean variable?

It returns the string 'boolean'.

intermediate

Why might you prefer is_*() functions over gettype() for type checking?

Because is_*() functions return a boolean (true/false), making it easier to write conditions, while gettype() returns a string that you must compare.

What does gettype(123) return in PHP?

A 'integer'

B 'string'

C 'number'

D 'int'

gettype() returns 'integer' for whole numbers.

Which function checks if a variable is a string in PHP?

A gettype()

B is_str()

C typeof()

D is_string()

is_string() returns true if the variable is a string.

Does PHP have a typeof operator like JavaScript?

A Yes, it works the same way

B No, PHP uses <code>gettype()</code> instead

C Yes, but it returns different values

D No, PHP does not support type checking

PHP uses gettype() and is_*() functions for type checking.

What will is_bool(true) return?

A null

B false

C true

D 1

is_bool() returns true if the variable is boolean.

Which of these is NOT a valid return value of gettype()?

A 'number'

B 'double'

C 'array'

D 'object'

'number' is not a valid return value; PHP uses 'integer' or 'double' instead.

Explain how to check the type of a variable in PHP and the difference between gettype() and is_*() functions.

Think about how PHP tells you what type a variable is and how you can test it in conditions.

Describe why PHP does not have a typeof operator and how you can achieve similar functionality.

Compare PHP and JavaScript type checking methods.

Practice

1. What does the PHP function gettype() return when called on a variable?

easy

A. A string describing the variable's type

B. An integer representing the type code

C. A boolean indicating if the variable is set

D. An object describing the variable

Solution

1. Step 1: Understand the purpose of gettype()

   The gettype() function returns the type of a variable as a string, such as "integer", "string", or "array".

2. Step 2: Compare options with gettype() behavior

   The option stating that it returns a string describing the variable's type is correct.

3. Final Answer:

   A string describing the variable's type -> Option A

4. Quick Check:

   gettype() = string description [OK]

Hint: Remember: gettype() always returns a string type name [OK]

Common Mistakes:

• Thinking gettype() returns a numeric code
• Confusing gettype() with isset()
• Assuming gettype() returns an object

2. Which of the following is the correct syntax to get the type of a variable $var using gettype() in PHP?

easy

A. gettype $var;

B. typeof $var;

C. typeof($var);

D. gettype($var);

Solution

1. Step 1: Recall correct function syntax in PHP

   PHP functions require parentheses around arguments, so gettype($var); is correct syntax.

2. Step 2: Check other options for syntax errors

   Syntax using typeof is invalid because it is not a PHP function. gettype $var; misses parentheses, which is invalid syntax.

3. Final Answer:

   gettype($var); -> Option D

4. Quick Check:

   Function call syntax = gettype($var) [OK]

Hint: Use parentheses with function calls in PHP [OK]

Common Mistakes:

• Using typeof instead of gettype()
• Omitting parentheses in function calls
• Confusing PHP syntax with JavaScript

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

$x = 3.14;
echo gettype($x);

medium

A. integer

B. double

C. float

D. string

Solution

1. Step 1: Identify the variable type

   The variable $x is assigned 3.14, which is a floating-point number.

2. Step 2: Understand gettype() output for floats

   In PHP, gettype() returns "double" for floating-point numbers, not "float".

3. Final Answer:

   double -> Option B

4. Quick Check:

   gettype(3.14) = double [OK]

Hint: Remember: PHP calls floats "double" in gettype() output [OK]

Common Mistakes:

• Expecting output to be "float" instead of "double"
• Confusing integer and float types
• Assuming gettype() returns "string" for numbers

4. Consider this PHP code snippet:

$value = true;
if (typeof($value) === 'boolean') {
    echo 'Boolean type';
} else {
    echo 'Not boolean';
}

What is the problem with this code?

medium

A. typeof is not a valid PHP function

B. Comparison operator === cannot be used with strings

C. Boolean values cannot be checked with typeof

D. The variable $value is not defined

Solution

1. Step 1: Check if typeof is a PHP function

   PHP does not have a built-in typeof() function; it uses gettype() instead.

2. Step 2: Analyze the impact of using typeof()

   Using typeof() causes a fatal error because the function does not exist.

3. Final Answer:

   typeof is not a valid PHP function -> Option A

4. Quick Check:

   typeof() invalid in PHP [OK]

Hint: Use gettype(), not typeof(), in PHP [OK]

Common Mistakes:

• Assuming typeof() exists in PHP like in JavaScript
• Thinking === cannot compare strings
• Ignoring variable initialization

5. In PHP 8.0+, the typeof operator returns a Type object instead of a string. Given this code:

$var = [1, 2, 3];
$type = typeof $var;
echo $type->name;

What will be the output?

hard

A. Type

B. object

C. error

D. array

Solution

1. Step 1: Verify typeof in PHP 8.0+

   PHP has no typeof operator or function in 8.0+ or any version; use gettype() instead.

2. Step 2: Predict code execution

   The undefined typeof causes a fatal error (e.g., "Call to undefined function"). No echo output.

3. Final Answer:

   error -> Option C

4. Quick Check:

   typeof invalid in PHP [OK]

Hint: PHP has no typeof; use gettype() [OK]

Common Mistakes:

• Believing typeof exists in PHP 8.0+
• Confusing PHP with JavaScript's typeof
• Expecting a Type object return