creating a simple exception for a class - php

Question

I am creating a class called ex: foo
class foo{
function __construct($arg){
if(empty($arg)){
throw new fooException('argument can not be empty');
}
}
}
I tried to create the class without passing anything through the constructor like this
try{
$o = new foo();
}catch(FooException $e){
echo $e->getMessage();
}
I am getting error Fatal error: Class 'FooException' not found in ..
I realize that, I need to extend maybe the error exception class, but there are no examples on how to do this in SO.

Answer 1

Here's an example of defining a custom Exception called FooException.
The class that follows it, TestException tests this custom exception.
<?php
/**
* Define a custom exception class
*/
class FooException extends Exception
{
// Redefine the exception so message isn't optional
public function __construct($message, $code = 0, Exception $previous = null) {
// some code
// make sure everything is assigned properly
parent::__construct($message, $code, $previous);
}
// custom string representation of object
public function __toString() {
return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
}
public function customFunction() {
echo "A custom function for this type of exception\n";
}
}
/**
* Create a class to test the exception
*/
class TestException
{
public $var;
const THROW_NONE = 0;
const THROW_CUSTOM = 1;
const THROW_DEFAULT = 2;
function __construct($avalue = self::THROW_NONE) {
switch ($avalue) {
case self::THROW_CUSTOM:
// throw custom exception
throw new FooException('1 is an invalid parameter', 5);
break;
case self::THROW_DEFAULT:
// throw default one.
throw new Exception('2 is not allowed as a parameter', 6);
break;
default:
// No exception, object will be created.
$this->var = $avalue;
break;
}
}
}
// Example 1
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (FooException $e) { // Will be caught
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // Skipped
echo "Caught Default Exception\n", $e;
}
// Continue execution
var_dump($o); // Null
echo "\n\n";
// Example 2
try {
$o = new TestException(TestException::THROW_DEFAULT);
} catch (FooException $e) { // Doesn't match this type
echo "Caught my exception\n", $e;
$e->customFunction();
} catch (Exception $e) { // Will be caught
echo "Caught Default Exception\n", $e;
}
// Continue execution
var_dump($o); // Null
echo "\n\n";
// Example 3
try {
$o = new TestException(TestException::THROW_CUSTOM);
} catch (Exception $e) { // Will be caught
echo "Default Exception caught\n", $e;
}
// Continue execution
var_dump($o); // Null
echo "\n\n";
// Example 4
try {
$o = new TestException();
} catch (Exception $e) { // Skipped, no exception
echo "Default Exception caught\n", $e;
}
// Continue execution
var_dump($o); // TestException
echo "\n\n";
?>
Source: http://www.php.net/manual/en/language.exceptions.extending.php
I modified it for your FooException

Answer 2

I see 2 things here, first, the exception you are throwing is called "fooException", and then, the one you are catching, is called "FooException", this is not correct, maybe a typo?. Another thing is, did you create a class named "FooException" and load it in your application?
require_once(path/to/FooExceptionClass.php);
Hope this helps.