php - Reference - frequently asked questions about PDO -

what this?

this list of asked questions regarding php data objects

why this?

as pdo has features unknown regular php user, questions regarding prepared statements , error handling in pdo quite frequent. so, place them can found.

what should here?

if question has been closevoted list, please find question below , apply fix code. idea take brief other questions, make prepared other common pitfalls.

the list

• pdo query fails can't see errors. how error message pdo?
• how can use prepared statements operator?
• how can create prepared statement in () operator?
• can use pdo prepared statement bind identifier (a table or field name) or syntax keyword?
• pdo prepared statement causes error in limit statement

see also

• reference - symbol mean in php?
• reference - error mean in php?
• reference - variable scope, variables accessible , “undefined variable” errors?

pdo query fails can't see errors. how error message pdo?

to able see database errors, 1 have set pdo errmode exceptions. exceptions better regular errors in many ways: contains stack trace, can caught using try..catch or handled using dedicated error handler. , unhandled, act regular php errors providing important information, following site-wide error reporting settings.

note setting mode connection option let pdo throw exceptions on connection errors too, important.
so, here example creating pdo connection right way:

$dsn = "mysql:host=$host;dbname=$db;charset=utf8"; $opt = array(     pdo::attr_errmode            => pdo::errmode_exception,     // other options  ); $pdo = new pdo($dsn, $user, $pass, $opt); 

connecting way, notified of database errors, occurred during query execution. note have able see php errors in general. on live site have peek error logs, so, settings have be

error_reporting(e_all); ini_set('display_errors',0); ini_set('log_errors',1); 

while on local development server it's ok make errors on screen:

error_reporting(e_all); ini_set('display_errors',1); 

and of course should never ever use error suppression operator (@) in front of pdo statements.

also, due many bad examples telling wrap every pdo statement try..catch block, have make distinct note:

do not use try..catch operator echo error message. uncaught exception excellent purpose, act same way other php errors - so, can define behavior using site-wide settings - so, you have error message without useless code. while unconditionally echoed error message may reveal sensitive information potential attacker, yet confuse honest visitor.

• a custom exception handler added later, not required. new users, recommended use unhandled exceptions, extremely informative, helpful , secure.
• use try..catch if going handle error - say, rollback transaction.