MySQL error handling using try/catch: PHP, MySQL

MySQL error handling using try/catch

Asked by: akohan

Hello group,

It seems try/catch error handling is not designed to handle MySQL errors and mostly is designed only for dealing with objects. The reason I'm asking is becuse following code still shows the error in its traditional way.

My concern is showing and do a graceful message/exit rather default error message.

It that right?

try {
 
   mysql_connect("localhost", "user1", "passwd") or die(mysql_error());   
   $selected = mysql_select_db("mydb") or die("Could not select/open MyDB database");
 
} catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}

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<?php function exception_error_handler($errno, $errstr, $errfile, $errline ) { throw new ErrorException($errstr, 0, $errno, $errfile, $errline); } set_error_handler("exception_error_handler"); try { mysql_connect("localhost", "user1", "passwd"); $selected = mysql_select_db("mydb"); } catch (Exception $e) { echo 'Caught exception: ', $e->getMessage(), "\n"; } ?>

Well exceptions are only caught if php encounters an standard error(e_notice, e_warning,etc.), while your above code only throws an error(E_Warning) on mysql_connect but mysql_select_db doesn't return any errors if that selected database doesn't exists thus won't be caught as an exception.

So the main difference is that with your above code you'll stop the script manualy by checking if the functions returns false but ErrorException will not check if the function returns false so it will not throw an exception(in my first post i explained that ErrorException only replace the standard errors).

You are able to build gracefull errors like below code

<?php
function exception_error_handler($errno, $errstr, $errfile, $errline ) {
 
if(stristr($errstr, "Can't connect to MySQL server")==TRUE)
{
		$error =<<<ERR
	<div align="center" style="font-family:'Times New Roman', Times, serif; font-size:16px">
			 Unable to connect to the database server at this time. Please contact your Administrator or try again.
		  </div>
ERR;
		throw new ErrorException($error);
		
} elseif(stristr($errstr, "Access denied for user")==TRUE)	{
		$error =<<<ERR
	<div align="center" style="font-family:'Times New Roman', Times, serif; font-size:16px">
			 MySql Username/Password is wrong. Please contact your Administrator or try again.
		  </div>
ERR;
		throw new ErrorException($error);
		
} else	{
		throw new ErrorException($errstr, 0, $errno, $errfile, $errline);
}
 
}
set_error_handler("exception_error_handler");
 
 
 
try {
 
   mysql_connect('localhost', 'user1', 'passwd');
   $selected = mysql_select_db("mydb");
 
} catch (Exception $e) {
    echo $e->getMessage();
}
 
?>

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MySQL error handling using try/catch

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