PHP - Boolean

In PHP, a boolean (bool) is a built-in scalar data type used to express truth values, which can be either True or False. Boolean literals use the constants True or False, which are case-insensitive.

Declaration and Usage

You can declare a boolean variable as follows:

$a = true;

Logical operators like <, >, ==, !=, etc., return boolean values.

Example:

$gender = "Male";
var_dump($gender == "Male");

Output:

bool(true)

Boolean Values in Control Statements

Boolean values are integral to control statements such as if, while, for, and foreach. The behavior of these statements depends on the true/false value returned by boolean expressions.

Example:

$mark = 60;

if ($mark > 50) {
   echo "pass";
} else {
   echo "fail";
}

Converting Values to Boolean

Use the (bool) casting operator to convert values to boolean. In a logical context, values are automatically interpreted as boolean.

• Non-zero numbers are considered true, except for 0 (+0.0 or -0.0) which is false.
• Non-empty strings are true, empty string "" is false.
• Non-empty arrays are true, empty array is false.

Example:

$a = 10;
echo "$a: ";
var_dump((bool)$a);

$a = 0;
echo "$a: ";
var_dump((bool)$a);

$a = "Hello";
echo "$a: ";
var_dump((bool)$a);

$a = "";
echo "$a: ";
var_dump((bool)$a);

$a = array();
echo "$a: ";
var_dump((bool)$a);

Output:

10: bool(true)
0: bool(false)
Hello: bool(true)
: bool(false)
Array: bool(false)

This diagram illustrates the flow of boolean handling in PHP, from declaration to usage in control statements and conversion of values to boolean.