php – What are the Try/Catch Blocks for and when should they be used?

Question:

I've been looking for some explanations on the subject, but I haven't found any that were simple and straightforward. My question is: What are the Try/Catch Blocks for and when should they be used?

Answer:

The try/catch is for handling exceptions, handling codes that may not be fully met and generate some exception/error.

The try able to recover errors that might occur in the code given in your block.
The catch in turn, handles the errors that happened.

Example:

try {
    //Esse código precisa de tratamento pois pode gerar alguma exceção
    $x = 1;
    if ($x === 1)
        throw new \Exception('X não pode ser 1');
} catch (\Exception $e) {
    var_dump($e->getMessage());
}

In addition we also have a block called finally (PHP 5.5 or higher), which provide instructions of what should be executed after the try/catch (usually releasing resources). If an exception is caught, the finally will be executed only after finishing the instructions given in catch . If no exceptions are thrown, the finally will be executed after the statements given in the try .

Example:

try {
    //Esse código precisa de tratamento pois pode gerar alguma exceção
    $variavel = AlgumaCoisa::pegarRecurso();
    if ($variavel->executarAlgumaCoisa())
        throw new \Exception('Erro: ' . $variavel->pegarErro());
} catch (\Exception $e) {
    var_dump($e->getMessage());
} finally {
    $variavel->liberarRecurso(); 
}

Finally, errors generated outside a try/catch can generate inconvenient messages for users who use your system. Let's take an example:

//Nada antes
throw new Exception('teste');
//Nada depois

If the code above is executed, it will generate a very nice error message on the screen

//Fatal error: Uncaught exception 'Exception' with message 'teste' in ...