Any PHP script is built out of a series of statements. A statement can be an assignment, a function call, a loop, a conditional statement of even a statement that does nothing (an empty statement). Statements usually end with a semicolon. In addition, statements can be grouped into a statement-group by encapsulating a group of statements with curly braces. A statement-group is a statement by itself as well. The various statement types are described in this chapter.
PHP defines a few constants and provides a mechanism for defining more at run-time. Constants are much like variables, but they have a slightly different syntax.
The pre-defined constants are __FILE__ and __LINE__, which correspond to the filename and line number being processed when they are encountered.
Example 6-1. Using __FILE__ and __LINE__ <?php
function report_error($file, $line, $message) {
echo "An error occured in $file on line $line: $message.";
}
report_error(__FILE__,__LINE__, "Something went wrong!");
?>
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You can define additional constants using the define() and undefine() functions.
Example 6-2. Defining Constants <?php
define("CONSTANT", "Hello world.");
echo CONSTANT; // outputs "Hello world."
undefine ("CONSTANT");
?>
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