Try-catch execution flow in PHP - Step-by-Step Execution

Concept Flow - Try-catch execution flow

Start

↓

Try block

↓

Exception?

No→Continue after try

Yes↓

Catch block

↓

Continue after catch

↓

End

The program tries to run code inside the try block. If an error happens, it jumps to the catch block. Then it continues after the catch.

Execution Sample

PHP

<?php
try {
  echo "Start\n";
  throw new Exception("Error happened");
  echo "End\n";
} catch (Exception $e) {
  echo "Caught: " . $e->getMessage() . "\n";
}
?>

This code prints 'Start', then throws an error, jumps to catch, and prints the error message.

Execution Table

Step	Action	Evaluation	Output
1	Enter try block	No exception yet	Start
2	Throw Exception	Exception thrown
3	Jump to catch block	Catch Exception	Caught: Error happened
4	End program	No more code

💡 Exception thrown at step 2, caught at step 3, program ends normally

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$e (Exception)	null	null	Exception object created	Exception object caught	Exception object caught

Key Moments - 2 Insights

Why does the code after 'throw' inside try not run?

Because at step 2 in the execution_table, the exception is thrown immediately, so the program jumps to the catch block and skips the remaining try code.

What happens if no exception is thrown in try?

The program runs all try code and skips the catch block, continuing after try normally, as shown by the 'No exception yet' evaluation in step 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is printed at step 1?

A Caught: Error happened

B Start

C End

D Nothing

💡 Hint

Check the Output column at step 1 in execution_table

At which step does the program jump to the catch block?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the Action and Evaluation columns in execution_table rows

If the 'throw' line is removed, what changes in the execution_table?

A Step 2 will not throw exception and step 3 catch block will be skipped

B Step 3 will still run catch block

C Output at step 1 changes

D Program will crash

💡 Hint

Refer to key_moments about what happens if no exception is thrown

Concept Snapshot

try {
  // code that might fail
} catch (Exception $e) {
  // code to handle error
}

- Code in try runs first
- If error (exception) happens, jump to catch
- Catch gets error info in $e
- After catch, program continues normally

Full Transcript

This example shows how PHP handles errors using try and catch. The program starts by running code inside the try block. When it reaches the throw statement, it creates an error and immediately stops running the try block. Instead, it jumps to the catch block where the error is caught and handled. The catch block prints the error message. After that, the program continues normally. If no error happens, the catch block is skipped. This flow helps programs handle problems without crashing.