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PHP - Boolean

In PHP, a Boolean is a simple data type that can hold one of two possible values: TRUE or FALSE. Boolean values are often used in control structures such as conditional statements and loops to determine the flow of execution based on certain conditions.

Defining Booleans

Booleans can be defined directly using the keywords true and false (case-insensitive).

Example:

php
<?php
        $isTrue = true;
        $isFalse = false;
        ?>

Evaluating Boolean Values

PHP automatically converts various types of values to Boolean in conditional statements. The following values are considered FALSE in a Boolean context:

  • The keyword false
  • The integer 0
  • The float 0.0
  • An empty string "" and the string "0"
  • An array with zero elements
  • An object with zero member variables (PHP 7.2 and earlier)
  • The special type NULL
  • A variable declared, but without a value (uninitialized)

All other values are considered TRUE.

Using Booleans in Conditional Statements

Booleans are typically used in conditional statements like if, else, elseif, and loops like while and for.

Example:

php
<?php
        $isTrue = true;
        
        if ($isTrue) {
            echo "This is true.";
        } else {
            echo "This is false.";
        }
        ?>

Boolean Operators

PHP supports several logical operators for Boolean values:

1. Logical AND (&& or and)

Returns true if both operands are true.

Example:

php
<?php
        $a = true;
        $b = false;
        
        $result = $a && $b; // false
        $result = $a and $b; // false
        ?>

2. Logical OR (|| or or)

Returns true if at least one of the operands is true.

Example:

php
<?php
        $a = true;
        $b = false;
        
        $result = $a || $b; // true
        $result = $a or $b; // true
        ?>

3. Logical NOT (!)

Negates the Boolean value.

Example:

php
<?php
        $a = true;
        
        $result = !$a; // false
        ?>

4. Logical XOR (xor)

Returns true if exactly one of the operands is true, but not both.

Example:

php
<?php
        $a = true;
        $b = false;
        
        $result = $a xor $b; // true
        ?>

Casting to Boolean

You can explicitly cast a variable to Boolean using (bool) or (boolean).

Example:

php
<?php
        $var = 1; // integer
        $boolVar = (bool)$var; // true
        ?>

Boolean Conversion

PHP converts various types to Boolean based on the rules mentioned earlier.

Example:

php
<?php
        $var1 = "";    // false
        $var2 = "0";   // false
        $var3 = 0;     // false
        $var4 = [];    // false
        $var5 = null;  // false
        $var6 = "Hello"; // true
        $var7 = 42;    // true
        
        echo (bool)$var1; // Output: false
        echo (bool)$var2; // Output: false
        echo (bool)$var3; // Output: false
        echo (bool)$var4; // Output: false
        echo (bool)$var5; // Output: false
        echo (bool)$var6; // Output: true
        echo (bool)$var7; // Output: true
        ?>

Checking Boolean Values

PHP provides the is_bool() function to check if a variable is a Boolean.

Example:

php
<?php
        $var = true;
        
        if (is_bool($var)) {
            echo "This is a Boolean.";
        } else {
            echo "This is not a Boolean.";
        }
        ?>

Summary:

Booleans in PHP are straightforward but essential for controlling the flow of a program. They are used extensively in conditional statements and loops to determine the truthiness of expressions. Understanding how PHP evaluates and manipulates Boolean values is fundamental for writing effective and efficient code.