Type casting syntax in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code with type casting?

Consider the following PHP code snippet. What will it output?

PHP

<?php
$value = "123abc";
$intValue = (int)$value;
echo $intValue;
?>

A 123

B 0

C 123abc

D Error

💡 Hint

When casting a string to int in PHP, it converts the initial numeric part.

PHP converts the string "123abc" to integer by reading the initial numeric characters until a non-digit is found. So it becomes 123.

❓ Predict Output

intermediate

What is the output when casting a float to int in PHP?

What will this PHP code print?

PHP

<?php
$floatVal = 3.99;
$intVal = (int)$floatVal;
echo $intVal;
?>

A 4

B Error

C 3.99

D 3

💡 Hint

Casting float to int truncates the decimal part.

When casting a float to int in PHP, the decimal part is removed (not rounded). So 3.99 becomes 3.

❓ Predict Output

advanced

What error does this PHP code raise?

What error will this PHP code produce?

PHP

<?php
$array = [1, 2, 3];
$intVal = (int)$array;
echo $intVal;
?>

A 1

B 0

C Fatal error: Uncaught Error: Object of class Array could not be converted to int

D Warning: Array to string conversion

💡 Hint

Arrays cannot be cast to int in PHP.

PHP throws a fatal error when trying to cast an array to int because this conversion is not allowed.

❓ Predict Output

advanced

What is the output of casting boolean to string in PHP?

What will this PHP code output?

PHP

<?php
$boolVal = true;
$strVal = (string)$boolVal;
echo strlen($strVal);
?>

A 4

B 1

C 0

D Error

💡 Hint

True converts to string "1" and false to empty string "".

Casting true to string results in "1" which has length 1.

❓ Predict Output

expert

What is the output of this complex type casting in PHP?

What will this PHP code output?

PHP

<?php
$value = "10 apples";
$floatVal = (float)$value;
$intVal = (int)$floatVal;
echo $intVal + 5;
?>

A 15

B 10

C 5

D Error

💡 Hint

Casting string to float reads initial number, then casting float to int truncates decimals.

"10 apples" cast to float becomes 10.0, then to int becomes 10. Adding 5 results in 15.

Practice

1. What does the following PHP code do?
$num = (int) "123";

easy

A. Converts the string "123" to an integer 123

B. Converts the integer 123 to a string

C. Throws a syntax error

D. Leaves the variable as a string

Solution

1. Step 1: Identify the type casting operation

   The code uses (int) before a string variable, which means it converts the string to an integer.

2. Step 2: Understand the conversion result

   The string "123" becomes the integer 123 after casting.

3. Final Answer:

   Converts the string "123" to an integer 123 -> Option A

4. Quick Check:

   Type casting (int) converts string "123" to integer 123 [OK]

Hint: Casting (int) changes strings of digits to numbers [OK]

Common Mistakes:

• Thinking it converts integer to string
• Expecting a syntax error
• Assuming the variable stays a string

2. Which of the following is the correct syntax to cast a variable $value to a float in PHP?

easy

A. $floatValue = (float) $value;

B. $floatValue = cast float $value;

C. $floatValue = float($value);

D. $floatValue = (float)$value[];

Solution

1. Step 1: Recall PHP type casting syntax

   PHP uses (type) before a variable to cast it, so (float) $value is correct.

2. Step 2: Check each option

   $floatValue = float($value); uses a function-like syntax which is invalid. $floatValue = cast float $value; uses invalid syntax. $floatValue = (float)$value[]; tries to cast an array element incorrectly.

3. Final Answer:

   $floatValue = (float) $value; -> Option A

4. Quick Check:

   Correct cast syntax is (float) $value [OK]

Hint: Use (type) before variable for casting in PHP [OK]

Common Mistakes:

• Using function call syntax like float($value)
• Writing cast without parentheses
• Adding invalid array brackets after cast

3. What is the output of this PHP code?

$a = "10 apples";
$b = (int) $a;
echo $b;

medium

A. Syntax error

B. 0

C. 10

D. 10 apples

Solution

1. Step 1: Understand casting string with numbers and text

   When casting a string starting with numbers to int, PHP converts the leading number part only.

2. Step 2: Apply casting to the string "10 apples"

   The string starts with "10", so (int) "10 apples" becomes integer 10.

3. Final Answer:

   10 -> Option C

4. Quick Check:

   String starting with digits casts to those digits as int [OK]

Hint: Casting string with leading digits to int keeps those digits [OK]

Common Mistakes:

• Expecting full string output
• Thinking casting fails with text
• Assuming zero because of text

4. Find the error in this PHP code snippet:

$value = "123.45";
$intValue = int($value);
echo $intValue;

medium

A. Missing semicolon after echo

B. int() is not a valid cast syntax in PHP

C. Variable $value is not defined

D. Casting float to int is not allowed

Solution

1. Step 1: Check the casting syntax used

   The code uses int($value), which looks like a function call but PHP does not have int() function for casting.

2. Step 2: Identify correct casting method

   PHP uses (int) $value to cast, not int($value).

3. Final Answer:

   int() is not a valid cast syntax in PHP -> Option B

4. Quick Check:

   Use (int) for casting, not int() function [OK]

Hint: Casting uses (int), not int() function [OK]

Common Mistakes:

• Using int() like a function
• Confusing casting with function calls
• Ignoring PHP casting syntax rules

5. Given the array $data = ["5", "3.14", "true", "false", "0"];, which PHP code correctly casts each element to its proper type (int, float, bool) using type casting syntax and stores results in $result?

hard

A. $result = [int($data[0]), float($data[1]), bool($data[2]), bool($data[3]), bool($data[4])];

B. $result = [(float)$data[0], (float)$data[1], (string)$data[2], (string)$data[3], (bool)$data[4]];

C. $result = [(int)$data[0], (int)$data[1], (bool)$data[2], (bool)$data[3], (int)$data[4]];

D. $result = [(int)$data[0], (float)$data[1], (bool)$data[2], (bool)$data[3], (bool)$data[4]];

Solution

1. Step 1: Analyze required casts for each element

   "5" should be int, "3.14" float, "true" and "false" to bool, "0" to bool.

2. Step 2: Check each option for correct casting syntax and types

   $result = [(int)$data[0], (float)$data[1], (bool)$data[2], (bool)$data[3], (bool)$data[4]]; uses correct (type) syntax and casts each element properly. $result = [int($data[0]), float($data[1]), bool($data[2]), bool($data[3]), bool($data[4])]; uses invalid function-like casts. $result = [(int)$data[0], (int)$data[1], (bool)$data[2], (bool)$data[3], (int)$data[4]]; casts "3.14" to int incorrectly. $result = [(float)$data[0], (float)$data[1], (string)$data[2], (string)$data[3], (bool)$data[4]]; casts "true" and "false" to string incorrectly.

3. Final Answer:

   $result = [(int)$data[0], (float)$data[1], (bool)$data[2], (bool)$data[3], (bool)$data[4]]; -> Option D

4. Quick Check:

   Use (type) syntax and correct types for each element [OK]

Hint: Use (type) before each element for proper casting [OK]

Common Mistakes:

• Using function calls instead of casting syntax
• Casting floats as int incorrectly
• Casting booleans as strings