PHP Booleans

A Boolean represents two possible states: TRUE or FALSE. Booleans are the core of all logic in programming—they allow your code to make decisions, run loops, and validate data.

1. Declaring Booleans

Assigning a boolean value is simple. Note that the keywords true and false are NOT case-sensitive in PHP, but lowercase is the industry standard.

<?php
    $isVisible = true;
    $hasError = false;
?>

2. Comparison Results

Most of the time, you don't create booleans manually; they are the result of a comparison using operators like ==, >, or <.

<?php
    $x = 10;
    $y = 5;

    var_dump($x > $y); // Outputs: bool(true)
    var_dump($x == $y); // Outputs: bool(false)
?>

3. The "Falsy" Rule

An essential concept in PHP is knowing which values automatically convert to FALSE when used in a logical test (like an if statement). These are known as "Falsy" values.

The following values are considered FALSE:

• The boolean false itself.
• The integer 0 (zero).
• The float 0.0 (zero).
• The empty string "".
• The string "0" (This is a unique PHP quirk!).
• An array with zero elements [].
• The special type NULL.

Everything else is considered TRUE.

<?php
    $name = "";
    if ($name) {
        echo "This will not run because empty string is false.";
    }
?>

Checking for Booleans

You can use the is_bool() function to check if a variable specifically contains a boolean value.

<?php
    $active = true;
    var_dump(is_bool($active)); // Outputs: bool(true)
?>

Key Points to Remember

• A Boolean has only two values: true or false.
• Booleans are the result of comparison operators.
• Empty strings, the number 0, and NULL are all considered false.
• Use is_bool() to verify if a variable is a boolean.
• Lowercase true/false is the preferred coding style.