19c02-2.php

介绍PHP5的给类型函数应用

<?php
// Extend the Exception class to create a 'less than' exception
class LessThanException extends Exception {
	// Create a variable to hold what the minimum number was:
	private $number;
	
	// Redefine the constructor to just accept the number.
	public function __construct($num) {
		// First save the number off
		$this->number = $num;
		
		// Now we need to call the parent constructor and pass on data
		parent::__construct("Number was less than {$num}");
	}
}

// Now also create a very similar Greater Than version:
class GreaterThanException extends Exception {
	// Create a variable to hold what the max number was:
	private $number;
	
	// Redefine the constructor to just accept the number.
	public function __construct($num) {
		// Save the number off
		$this->number = $num;
		
		// Now we need to call the parent constructor and pass on data
		parent::__construct("Number was greater than {$num}");
	}
	
	// Declare a function that will return what the number was:
	public function thanWhat() {
		return $this->number;
	}
}

// Now we can begin using these:

// Begin a try block so that we can catch any exceptions that happen:
try {
	// Generate a random number from 10 to 50
	$num = rand(10,50);
	
	// If the number is less than 25 we aren't happy:
	if ($num < 25) {
		// Ok, it was less than, so throw a less than exception:
		throw new LessThanException(25);
	}
	
	// Also the number shouldn't be greater than 42
	if ($num > 42) {
		// This time use the greater than exception.
		throw new GreaterThanException(42);
	}
}
// First try to catch less than errors:
catch (LessThanException $le) {
	// We caught the exception, this is really unacceptable, so error out:
	die('<p>LESS THAN ERROR: ' . $le->getMessage() . "</p>\n");
}
// Now let's try to catch the greater than errors:
catch (GreaterThanException $ge) {
	// If it was greater than, let's just invisibly reset it to what our
	// max really was:
	$num = $ge->thanWhat();
}

// We are happy with the number now so print it out.
echo "<p>Our new number is: {$num}</p>\n";
?>