Question

i am trying to understand the use of exceptions in PHP.. How they work and when to use them… The basic structure below, is the the correct method.. It seems somewhat bloated to me?

Thanks in advance for any advise or help..

<?php

class APIException extends Exception 
{
    public function __construct($message)
    {
        parent::__construct($message, 0);
    }

    public function __toString()
   {
        echo('Error: ' . parent::getMessage());
    }

   public function __toDeath()  
   {
      die("Oops: ". parent::getMessage());
   }
}

?>

<?php

require_once('exception.class.php');

class auth extends base
{
   /* 
    * User functions 
    */ 

   public function user_create($args='')
   {
      try
      {
         if ( !isset($arg['username']) || !isset($arg['password']) || 
              !isset($arg['question']) || !isset($arg['answer']) )
         {
            throw new APIException('missing variables, try again');
         }
      }
      catch (APIException $e)
      {
         $e->__toString();
      }

      try
      {
         if ( $this->user_exists() ) 
         {
            throw new APIException('user already exists');
         }
      }
      catch (APIException $e)
      {
         $e->__toString();
      }
   }

   protected function user_exists($name)
   {
      // Do SQL Query 
      try
      {
         $sql = "select * from user where username='$user'";
         if (!mysql_query($sql))
         {
            throw new APIException('SQL ERROR');
         }
      }
      catch (APIException $e)
      {
         $e->__toDeath();
      }
   }
}

?>

Answer 1

No, you’re not using them correctly. Take a look at this

public function user_create($args='')
{
  try
  {
     if ( !isset($arg['username']) || !isset($arg['password']) || 
          !isset($arg['question']) || !isset($arg['answer']) )
     {
        throw new APIException('missing variables, try again');
     }
  }
  catch (APIException $e)
  {
     $e->__toString();
  }
  //snip...

When you throw new APIException('missing variables, try again');, it will just be caught by catch (APIException $e).

One of the points of exceptions is so that you can tell code calling the function that something went wrong. A more proper usage might look something like this.

public function user_create($args='')
{
   if ( !isset($arg['username']) || !isset($arg['password']) || 
        !isset($arg['question']) || !isset($arg['answer']) )
   {
      throw new APIException('missing variables, try again');
   }
  //snip...

// elsewhere
try {
  $foo->user_create('bar');
} catch(APIException $e) {
  // handle error here
  // log_error($e->getCode(), $e->getMessage());
}

Notice that the you use the try/catch block when you call user_create. Not within user_create.