Type juggling in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of loose comparison with string and integer

What is the output of this PHP code?

$a = "10 apples";
$b = 10;
var_dump($a == $b);

PHP

$a = "10 apples";
$b = 10;
var_dump($a == $b);

A int(10)

B bool(false)

C bool(true)

D string(9) "10 apples"

💡 Hint

PHP converts the string to a number when using ==.

When comparing a string to a number with ==, PHP converts the string to a number until it hits a non-numeric character. "10 apples" becomes 10, so 10 == 10 is true.

❓ Predict Output

intermediate

Result of adding string and integer

What is the output of this PHP code?

$x = "5 cats" + 3;
var_dump($x);

PHP

$x = "5 cats" + 3;
var_dump($x);

A int(53)

B int(8)

C float(8.0)

D string(5) "5 cats"

💡 Hint

PHP converts strings to numbers when using arithmetic operators.

The string "5 cats" is converted to the number 5, then 3 is added, resulting in 8 as an integer.

❓ Predict Output

advanced

Output of loose comparison with boolean and string

What is the output of this PHP code?

$a = false;
$b = "0";
var_dump($a == $b);

PHP

$a = false;
$b = "0";
var_dump($a == $b);

A bool(true)

B bool(false)

C int(0)

D string(1) "0"

💡 Hint

When comparing boolean and string, PHP converts string to boolean.

The string "0" is considered false in boolean context, so false == false is true.

❓ Predict Output

advanced

Output of strict comparison with integer and string

What is the output of this PHP code?

$a = 0;
$b = "0";
var_dump($a === $b);

PHP

$a = 0;
$b = "0";
var_dump($a === $b);

A bool(false)

B bool(true)

C int(0)

D string(1) "0"

💡 Hint

Strict comparison checks both value and type.

The integer 0 and string "0" have different types, so === returns false.

❓ Predict Output

expert

Output of arithmetic with null and string

What is the output of this PHP code?

$a = null;
$b = "10";
$c = $a + $b;
var_dump($c);

PHP

$a = null;
$b = "10";
$c = $a + $b;
var_dump($c);

A string(2) "10"

B TypeError

C int(0)

D int(10)

💡 Hint

Null is treated as zero in arithmetic operations.

Null is converted to 0, string "10" is converted to 10, sum is 10 as integer.