language-construct

I saw this today in some PHP code: $items = $items ?: $this->_handle->result('next', $this->_result, $this); I'm not familiar with the ?: operator being used here. It looks like a ternary operator, but the expression to evaluate to if the predicate is true has been omitted. What does it mean? BalusC It evaluates to the left operand if the left operand is truthy , and the right operand otherwise. In pseudocode, foo = bar ?: baz; roughly resolves to foo = bar ? bar : baz; or if (bar) { foo = bar; } else { foo = baz; } with the difference that bar will only be evaluated once. You can also use

I know that include , isset , require , print , echo , and some others are not functions but language constructs. Some of these language constructs need parentheses, others don't. require 'file.php'; isset($x); Some have a return value, others do not. print 'foo'; //1 echo 'foo'; //no return value So what is the internal difference between a language construct and a built-in function? (This is longer than I intended; please bear with me.) Most languages are made up of something called a "syntax": the language is comprised of several well-defined keywords, and the complete range of expressions