Re: phpbuilder - Error Handling

> Hi all, > > here some ideas on error handling based on what I have seen in the > phpbuilder article > http://www.phpbuilder.com/columns/sean20000712.php3?page=3. I > guess it > shown only a small subset of your ideas Stig, does it? > > I like the idea of creating error objects very much and I played with it > in my last project. I adopted quite a lot of the java way. All error > classes are inherited from a common baseclass "exception". > > instance variables: > > $CLASSNAME - overriden, used to classify exceptions (IO, User, ...) > > $ERROR_MESSAGE_PREFIX - overriden, some prefix added to the exception > > $ERROR_PREPEND - some prepend and append for PHP3 users that do not > $ERROR_APPEND - have trigger_error() to customize the output > > $message - error message itself > $file - Filename where the error occured > $line - Line number where the error occured, method name is > not neccessary as long as you have the line number > > > $DIE_ON_ERROR - for debugging purpose it should be there > $AUTO_PRINT_ERROR - same as $DIE_ON_ERROR > > $LEVEL - error level used when trigger_error() gets called > $TRIGGER_ERROR - turns the call to trigger_error() on and off > > > I like having $DIE_ON_ERROR and $AUTO_PRINT_ERROR very much because it > makes debugging easy. Just turn it on an you'll see all messages. All > other variables are self explaining. > > methods: > > void constructor ( string $message, [string $file, int $line]) > > Sets some instance variables (message, file, line) and > calls trigger_error(), printLocalizedMessage() and die() > if necessary. > > string getMessage( void ) > > Returns the current error message. Uses ERROR_PREPEND, > ERROR_MESSAGE_PREFIX, message and ERROR_APPEND to > build the message. > > string getLocalizedMessage ( void ) > > Same as getMessage() plus line numbwe and filename. > > string getType( void ) > > Returns the $CLASSNAME. The classname should > always start with "Exception" or maybe "Error" > followed by a descriptive name. The $CLASSNAME > allows you to distinguish beetween a valid > return type and an error... > > > What does a derived class MyPackageException" look like? > > instance variables: > > $CLASSNAME = "ExceptionMyPackage"; > $ERROR_MESSAGE_PREPEND = "Error in my package: "; > $LEVEL = USER_ERROR; > > [$ERROR_PREPEND] > [$ERROR_APPEND] > > methods: > > void constructor ( string $message [, string $file, int $line] ) > > Just calls the constructor of the base class. > > > How do I "throw" an error? > > All my classes that might "throw" an error have a public instance > variables $err which holds the last exception object. Whenever an error > occurs the method saves the exception in $this->err and tries to return > some usefull value (false, empty array etc.) to preevent errors that > appear because an unexpected datatype gets returned. Anyway this is not > necessary for PEAR. Simply do: 'return MyPackageException("trouble > somewhere", __FILE__, __LINE__);'. > > How do I "catch" an error? > > $ok = DB::connect(); > if ( is_object($ok) && "Exception" == substr(get_classname($ok), ??end > of beginning?? ) ) { > $msg = $ok->getLocalizedMessage(); > # $ok->printLocalizedMessage(); > } > Easier yet, have DB:: (or whatever class) provide a method that checks whether or not it is an error object (we have something like that now): $ok = DB::connect(..); if (DB::isError ($ok)) { /* .. */ } -Sterling