> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# PHP bool
A `bool` (boolean) is a scalar data type in PHP that represents a logical truth value, strictly capable of holding one of two states: `true` or `false`.
The boolean constants in PHP are case-insensitive.
```php theme={"dark"}
$valid = true;
$active = FALSE; // Case-insensitive, though lowercase is the PSR-12 standard
```
## Type Casting and Coercion
PHP is a dynamically typed language and frequently performs implicit boolean coercion during logical operations. Explicit casting is executed using the `(bool)` or `(boolean)` cast operators.
```php theme={"dark"}
$explicitCast = (bool) $variable;
```
## Falsy Values
When a value is implicitly coerced or explicitly cast to a `bool`, PHP evaluates most values as `true` (truthy), with a specific set of exceptions that evaluate to `false` (falsy).
The following standard values evaluate to `false`:
```php theme={"dark"}
(bool) false; // The boolean false itself
(bool) 0; // Integer zero
(bool) 0.0; // Float zero (and -0.0)
(bool) ""; // Empty string
(bool) "0"; // String containing exactly the character "0"
(bool) []; // Array with zero elements
(bool) null; // NULL value (including unset variables)
```
*Note:* While almost all other values evaluate to `true` (including the string `"false"`, the string `"0.0"`, negative integers, and empty `stdClass` objects), there are exceptions for internal objects that overload their casting behavior. For example, a `SimpleXMLElement` object created from an empty XML element without attributes evaluates to `false`.
## String Representation
When a `bool` is cast to a string—such as when passed to an `echo` or `print` statement—PHP handles the conversion asymmetrically:
```php theme={"dark"}
$trueStr = (string) true; // Evaluates to the string "1"
$falseStr = (string) false; // Evaluates to an empty string ""
echo true; // Outputs the string "1"
echo false; // Outputs an empty string ""
```
## Type Checking
To verify if a variable is strictly of the `bool` type without triggering implicit type coercion, use the built-in `is_bool()` function. To verify if a variable holds a specific boolean value without coercion, use the strict comparison operators (`===` / `!==`).
```php theme={"dark"}
$var = false;
$intVar = 1;
// Checking type
is_bool($var); // Returns true (it is of type bool)
is_bool($intVar); // Returns false (it is an integer)
// Checking strict value
$var === false; // Returns true (strict type and value check)
$intVar === true; // Returns false (strict type and value check)
// Loose comparison
$intVar == true; // Returns true (loose comparison triggers coercion)
```
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