Managing Errors

Managing errors in any application is very important, 0:00 especially when it comes to database errors. 0:03 We will manage this by wrapping our code that communicates with 0:06 the database within a try catch block. 0:08 Continuing where we left off, we have created our PDO object successfully. 0:12 And then I demonstrated how we can break that, so, we're gonna go ahead and 0:17 break that again. 0:21 So, I'm gonna add a few more A's back in and 0:22 see how we can handle these errors and exceptions. 0:25 Let's go ahead and refresh this. 0:28 And now we'll see we have a fatal error, uncaught exception. 0:30 Well, we don't want that to happen. 0:34 And if you recall from object-oriented code practice. 0:35 We have a lot of tri-catch statements when were' trying to catch exceptions and 0:39 handle errors. 0:42 So that's what we're gonna do, we're gonna handle this PDL exception, 0:44 by catching any general exceptions in our script. 0:47 So head back over to the index.php file. 0:51 And then here we're gonna surround any connection to the database. 0:54 So here where we're creating our new database, 0:58 we're gonna actually surround that in a tri-block. 1:01 So tri, and then open and close are curly braces. 1:05 Then we have a catch. 1:10 Open and close parens. 1:13 And then open and close our curly braces. 1:16 Now, this is try catch block. 1:18 Inside of here, we're gonna try any code that we wanna run. 1:20 And if it fails out or has an exception, we want to catch that exception. 1:25 So here we just simply put the class that we want to catch, 1:30 which is a PDO Exception, or we can use the parent class to catch any exception. 1:33 So, we'll type in Exception with a capital E. 1:39 And then the next argument is the actual exception object that gets 1:44 thrown when the error happens. 1:49 So that one we'll just call it dollar sign e for exception. 1:51 Now we want to take this code here on line 11. 1:55 In fact we'll do line 11, 12. 1:57 We'll just copy it all. 2:00 And we'll put it inside of our try block. 2:03 So that way anything inside of 2:07 here will happen only if the succesful database object is created. 2:09 So the other half of this coin here or the other side of 2:15 this coin is to actually put something in here for our exception when that happens. 2:18 So right now I'm just gonna echo a string. 2:24 In that string let's say, sorry, the connection was not successful. 2:27 Okay? 2:37 And then I also don't want it to continue so I'll add another die statement here. 2:38 [BLANK_AUDIO] 2:42 Close it with a semicolon. 2:44 Save our file. 2:46 And I'm gonna refresh. 2:47 So instead of it throwing an uncalled exception, now it says, 2:49 sorry the connection was not successful. 2:52 Much cleaner, much nicer, no weird dumps to the screen about our code. 2:53 Exactly what we want. 2:58 Now to make sure it works, we're gonna go ahead and fix our error and then 2:59 back in here, save our file, and then let's redo our preview. 3:07 And now we have our PDO object. 3:13 Before we continue on we do want to do 2 more things to our tri-catch block or 3:16 to our PDO object and 3:21 then our actual exception to make it a little bit more informative for us. 3:23 So let's go ahead over to a new tab and let's open up the exception class. 3:28 We're gonna go ahead and do that. 3:33 I'm just gonna type in exception.php and 3:35 here we have exception, which shows us the actual exception class. 3:38 If we scroll down here, 3:44 we'll see that we have several different methods that we can use. 3:45 The one that we're going to want is get message, which if we click on 3:48 get message information it'll just say it gets the exception message, and 3:53 returns the exception message as a stray. 3:58 Head back over to your code, here I'm going to modify line 11, 4:01 I'm going to actually get rid of everything there just to echo. 4:05 I'm gonna pass through the actual exception object. 4:09 Just dollar sign e. 4:11 And then an object operator. 4:14 So that's a dash and a greater than symbol. 4:16 Looks like an arrow pointing to the right. 4:18 And that is how we tell it that we want to run a method. 4:20 The method that we're gonna run is get message. 4:23 So get and then capital m message. 4:26 And remember it is a method, or also a function, so 4:31 that means to call a function, we need to use the open and close parentheses. 4:34 So we'll go ahead and do that. 4:39 And then close it, save, and now let's refresh and see what the difference is. 4:41 Okay, connection successful, so I'll go in here, break it again. 4:47 Save our file, then refresh. 4:53 And so now it actually gives us an informative message more than just sorry, 4:56 I can't connect. 5:00 It actually tells you SQL state hey, we're unable to open the database file. 5:01 All right, so that tells us we can open the file may be we did a mistake in 5:06 our connection string, which now we know we did, so I'll go and 5:10 close that out and then hit Save. 5:13 Okay, the final step, the last thing that we want to do, is a command on the actual 5:16 PDO object itself or a method on the PDO object itself. 5:22 So we need to go ahead and 5:26 open up a new tab to search for the actual PHP PDO object. 5:28 So we'll do PDO class. 5:33 Then the PHP PDO class is in the manual. 5:36 Okay and if you scroll down here you'll see that 5:40 there are several different methods. 5:42 The one that we're interested in is setattribute. 5:45 So we say, set attribute. 5:49 And then in here, you'll see there are several constants or 5:51 the actual attributes that you can change. 5:54 That's here in the header. 5:57 So you'll see attribute case, and then attribute error mode. 5:58 So attribute error mode or the error reporting is what we want to modify. 6:02 So we wanna, scroll down a little bit more here. 6:08 We wanna modify this so that the error mode, when that happens, 6:10 anything that happens at all instead of silencing them or having a little warning. 6:14 We actually wanna set it to throw exception. 6:19 So no matter what the error is, we're gonna throw an exception. 6:22 So let's go ahead and do that by calling set 6:26 attribute on our actual PDO object, or the dollar sign DB. 6:30 So I'll head back over to our index.php file and we'll do it directly underneath. 6:34 So we're gonna get rid of this, and we don't need this guy anymore. 6:41 And then here, we're gonna do $db, object operator to setAttribute. 6:47 All right, and then close that line with a semicolon. 6:56 Now if you go back to where we were in the manual. 6:59 You'll see that we have the attribute and then the value. 7:02 So, our attribute that we're gonna set, copy this constant here, 7:05 and we're gonna paste that in. 7:10 That's our first argument. 7:14 Then we're gonna add a comma and 7:15 our second argument is the mode that we want to set it to. 7:17 And that would be PDO error mode exception. 7:21 Copy that paste it in. 7:26 Hit Save, and then I'm gonna do my preview just to make sure it's all good. 7:28 Okay, we didn't do the var dump, so we wouldn't see anything different, but 7:34 there's no errors, no exceptions, nothing dying out. 7:38 It seems like we're right where we wanna be. 7:41 Let's go ahead and close this guy out. 7:43 And then go back and review here. 7:46 So we've added a try catch statement to make sure there are any exceptions that 7:48 happen on the PDO connection string, will throw an error message to us and 7:52 then die out the script. 7:58 And then we also after creating the new PDO object, 7:59 we have sat the error mode attribute of the PDO object or 8:03 the DB object, to throw all exceptions for any kind of error that happens. 8:07 Next up we wanna run some queries and see what films are in our database. 8:13