Boolean Constants

true and false are the only two Boolean values treated as constants. A simple Boolean value can be a simple expression like the following:

if (true) {
    echo "I love programming.";
} else {
    echo "I hate programming.";
}

If the statement within parentheses results in true, then the true block should be executed; otherwise, the false block should.

Alternatively, we could write the following expression:

if (false) {
    echo "I hate programming.";
} else {
    echo "I love programming.";
}

Both approaches output I love programming..

In the preceding examples, we used the if…else control statement, which we are going to discuss a little later in this chapter.