The boolean expresses the truth value. The Boolean represents two possible values: TRUE or FALSE. True can be given a value of 1, and False is given a value of zero.
To specify a boolean literal, use the constants TRUE or FALSE. Both are case-insensitive. It means that TRUE is equal to true and FALSE is equal to false. So it can be written as
true === TRUE and false === FALSE
Example 1: This example display the value of uppercase and lowercase boolean.
<?php // PHP program to illustrates // boolean value   // Declare a variable and initialize it $boolean = TRUE;   // Display the value of variable echo $boolean . "\n";   // Declare a variable and initialize it $boolean = true;   // Display the value of variable echo $boolean;   ?> |
Output:
1 1
Example: This example compare the uppercase and lowercase boolean value.
<?php // PHP program to illustrates // boolean value   // Declare a variable and initialize it $var1 = TRUE; $var2 = true;   // Check both boolean value is same or not if($var1 == $var2)     echo "TRUE and true both are same \n"; else    echo "TRUE and true both are different \n";   // Declare a variable and initialize it $var1 = FALSE; $var2 = false;   // Check both boolean value is same or not if($var1 == $var2)     echo "FALSE and false both are same \n"; else    echo "FALSE and false both are different \n"; ?> |
Output:
TRUE and true both are same FALSE and false both are same
