How to efficiently use try...catch blocks in PHP

I have been using try..catch blocks in my PHP code, but I'm not sure if I've been using them correctly.

For example, some of my code looks like:

 try {
      $tableAresults = $dbHandler->doSomethingWithTableA();
      $tableBresults = $dbHandler->doSomethingElseWithTableB();
 } catch (Exception $e) {
      return $e;
 }

So I'm grouping multiple database operations in the same try/catch block because if any exception occurs in any of the transaction, I will be able to handle it.

I'm doing it that way because I think that it's more readable and efficient than:

 try {
       $tableAresults = $dbHandler->doSomethingWithTableA();
 } catch (Exception $e) {
       return $e;
 }
 try {
       $tableBresults = $dbHandler->doSomethingWithTableB();
 } catch (Exception $e) {
       return $e;
 }

Although, I'm not sure if what I'm doing is a good practice or just a lazy way to catch exceptions.

My assumption is that only if an exception requires special handling, it should have its own try/catch block, otherwise grouping them in the same try/catch should be ok.

So my question(s) are:

Is there any advantage of using try/catch blocks per database transaction? or can I still group multiple database transactions in the same try/catch block with no problem at all?

Is it ok to nest try/catch blocks? Thanks!

EDIT

The return statement was primarily for demonstration purposes only, but I'm also using returns in catch() because I'm making an AJAX request to that method, and Javascript is expecting a JSON object, then if an exception occurs I return an empty JSON encoded array. I just thought that It wouldn't add any value to put specific code in my example.

Solution 1:

Important note

The following discussion assumes that we are talking about code structured as in the example above: no matter which alternative is chosen, an exception will cause the method to logically stop doing whatever it was in the middle of.

As long as you intend to do the same thing no matter which statement in the try block throws an exception, then it's certainly better to use a single try/catch. For example:

function createCar()
{
    try {
      install_engine();
      install_brakes();
    } catch (Exception $e) {
        die("I could not create a car");
    }
}

Multiple try/catch blocks are useful if you can and intend to handle the failure in a manner specific to what exactly caused it.

function makeCocktail()
{
    try {
        pour_ingredients();
        stir();
    } catch (Exception $e) {
        die("I could not make you a cocktail");
    }

    try {
        put_decorative_umbrella();
    } catch (Exception $e) {
        echo "We 're out of umbrellas, but the drink itself is fine"
    }
}

Solution 2:

For posterity sake,the answer maybe too late.You should check for the return value of the variable and throw an exception. In that case you are assured that the program will jump from where the exception is being raised to the catch block. Find below.

try{
   $tableAresults = $dbHandler->doSomethingWithTableA();
   if (!tableAresults) 
     throw new Exception('Problem with tableAresults');

  $tableBresults = $dbHandler->doSomethingElseWithTableB();
   if (!tableBresults) 
     throw new Exception('Problem with tableBresults');
} catch (Exception $e) {
    echo $e->getMessage();

}