Non-looping conditionals: ternary ?

ternary.php

/**
 * O'Reilly p.82 Expressions and Control Flow
 * evaluates expression and
 * executes two stmts: one when expression is T and one when F
 * 
 * 1st stmt:  when expression is true
 * 2nd stmt:  when expression if false
 */
 $fuel = 1.00000000000001;
echo $fuel <= 1 ? "<p>Better stop for gas</p>" : "<p>Keep driving</p>";

/**
 * Concise way to keep track of the largest value as a program progresses.
 * Or testing whether var is set before passing to function.
 * Preferable syntax for short comparisons.
 */
$set = null;
$not_set = '<p>Nope... not set :( </p>';
echo $set = isset( $set ) ? $set : $not_set; ?>