Boolean type behavior in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What values are considered true in PHP when converted to boolean?

In PHP, any non-zero number, non-empty string (except "0"), non-empty array, and objects are considered true when converted to boolean.

beginner

Which values are considered false in PHP when converted to boolean?

The following values are considered false: false, integer 0, float 0.0, empty string "", string "0", empty array [], and null.

intermediate

How does PHP treat the string "0" in a boolean context?

The string "0" is treated as false in PHP boolean context, even though it is a non-empty string.

beginner

What happens when you use the boolval() function on different types in PHP?

The boolval() function converts any value to its boolean equivalent following PHP's rules: zero, empty, or null values become false; others become true.

intermediate

Explain the difference between == and === when comparing booleans in PHP.

The == operator compares values after type juggling, so 0 == false is true. The === operator compares both value and type, so 0 === false is false.

Which of these values is considered false in PHP boolean context?

A "false" (string)

B 1 (integer one)

C "0" (string zero)

D [1, 2, 3] (non-empty array)

The string "0" is considered false in PHP boolean context, while the others are true.

What does boolval(0.0) return in PHP?

A false

B null

C true

D 0

0.0 is treated as false when converted to boolean.

Which operator checks both value and type in PHP?

A ==

B ||

C !=

D ===

The === operator checks both value and type equality.

What is the boolean value of an empty array [] in PHP?

A true

B false

C null

D Depends on context

An empty array is considered false in boolean context.

Which of these is NOT considered false in PHP?

A "false" (string)

B "" (empty string)

C 0

D null

The string "false" is a non-empty string and is considered true.

Describe which values PHP treats as false in boolean context and why this might be surprising.

Think about zero, empty, and null values.

Explain the difference between == and === when comparing booleans in PHP with examples.

Focus on type comparison.