Throw exception and continue php

Question

You can, but I will warn: many consider this method quite evil.

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Table of Contents
Global exception handler
Does throwing an exception stop execution PHP?
Does PHP have try catch?
What is an exception how you can handle multiple exceptions in PHP?
Does throw return PHP?

// https://stackoverflow.com/a/66377817/578023
function is_same(&$a, &$b): bool {
    $_ = [ &$a, &$b ];
    return
        \ReflectionReference::fromArrayElement($_, 0)->getId() ===
        \ReflectionReference::fromArrayElement($_, 1)->getId();
}

function attempt_risky_action($collection){
    $cursor=NULL;
    $resuming = false;
    
    resume:
    try{
        foreach($collection as $item){
            if($resuming && !is_same($cursor,$item) ){
                continue;                   // some things have better ways to skip ahead, especially an array index
            }
            else {
                $resuming = false;
                $cursor=&$item;             // main concept is to remember where you are in the iteration
            }                               // in some situation you may have to use references,  &item
            

            // your normal loop here
            .
            .
            .
        }
    }   catch( Exception $e){
        $resuming = repair_something($e, $collection);      // returns false if your repair ran out of ideas
        if($resuming)
            goto resume;
    }
    
    unset($cursor);
    
}

Ideally it would be best to wrap the unset($cursor); call in a finally{} block, but frankly I'm not sure how that plays with goto off hand.

If it executes because goto broke the flow then you will need some conditional logic, so the cursor still exists. If you have a return statement inside the loop you must use a finally block for call to unset($cursor) -- or cause a memory leak.

Then again, while less exciting, you can do this same trick by just nesting your whole loop in do{ try/catch } while($resuming). While that is not LITERALLY reversing your execution, it does exactly the same effect without risking a goto.

is_same() from https://stackoverflow.com/a/66377817/578023

function attempt_risky_action($collection){
    $cursor=NULL;
    $resuming = false;
    
    do{
        try{
            foreach($collection as $item){
                if($resuming && !is_same($cursor,$item) ){
                    continue;   
                }
                else {
                    $resuming = false;
                    $cursor=&$item;
                }

                // your loop here
            }
        }   catch( Exception $e){
            $resuming = repair_something($e, $collection);      // returns false if your repair ran out of ideas
        }
        finally{ 
            if(!$resuming){
                unset($cursor); 
            }
        }
    } while($resuming);
}

A last method, not pictured; you can use PHP's reset(), prev(), current(), next(), end() faculties

These will allow you instead to simply have your try/catch block inside a code block that iterates as a loop would -- then use prev() in the catch to try again.

PHP has an exception model similar to that of other programming languages. An exception can be thrown, and caught ("catched") within PHP. Code may be surrounded in a try block, to facilitate the catching of potential exceptions. Each try must have at least one corresponding catch or finally block.

If an exception is thrown and its current function scope has no catch block, the exception will "bubble up" the call stack to the calling function until it finds a matching catch block. All finally blocks it encounters along the way will be executed. If the call stack is unwound all the way to the global scope without encountering a matching catch block, the program will terminate with a fatal error unless a global exception handler has been set.

The thrown object must be an instance of the Exception class or a subclass of Exception. Trying to throw an object that is not will result in a PHP Fatal Error.

As of PHP 8.0.0, the throw keyword is an expression and may be used in any expression context. In prior versions it was a statement and was required to be on its own line.

`catch`

A catch block defines how to respond to a thrown exception. A catch block defines one or more types of exception or error it can handle, and optionally a variable to which to assign the exception. (The variable was required prior to PHP 8.0.0.) The first catch block a thrown exception or error encounters that matches the type of the thrown object will handle the object.

Multiple catch blocks can be used to catch different classes of exceptions. Normal execution (when no exception is thrown within the try block) will continue after that last catch block defined in sequence. Exceptions can be thrown (or re-thrown) within a catch block. If not, execution will continue after the catch block that was triggered.

When an exception is thrown, code following the statement will not be executed, and PHP will attempt to find the first matching catch block. If an exception is not caught, a PHP Fatal Error will be issued with an "Uncaught Exception ..." message, unless a handler has been defined with set_exception_handler().

As of PHP 7.1.0, a catch block may specify multiple exceptions using the pipe (|) character. This is useful for when different exceptions from different class hierarchies are handled the same.

As of PHP 8.0.0, the variable name for a caught exception is optional. If not specified, the catch block will still execute but will not have access to the thrown object.

`finally`

A finally block may also be specified after or instead of catch blocks. Code within the finally block will always be executed after the try and catch blocks, regardless of whether an exception has been thrown, and before normal execution resumes.

One notable interaction is between the finally block and a return statement. If a return statement is encountered inside either the try or the catch blocks, the finally block will still be executed. Moreover, the return statement is evaluated when encountered, but the result will be returned after the finally block is executed. Additionally, if the finally block also contains a return statement, the value from the finally block is returned.

Global exception handler

If an exception is allowed to bubble up to the global scope, it may be caught by a global exception handler if set. The set_exception_handler() function can set a function that will be called in place of a catch block if no other block is invoked. The effect is essentially the same as if the entire program were wrapped in a try-catch block with that function as the catch.

Notes

Note:
Internal PHP functions mainly use Error reporting, only modern Object-oriented extensions use exceptions. However, errors can be easily translated to exceptions with ErrorException. This technique only works with non-fatal errors, however.
Example #3 Converting error reporting to exceptions
function exceptions_error_handler($severity, $message, $filename, $lineno) { throw new ErrorException($message, 0, $severity, $filename, $lineno); }set_error_handler('exceptions_error_handler'); ?>

Examples

Example #4 Throwing an Exception

function inverse($x) { if (!$x) { throw new Exception('Division by zero.'); } return 1/$x; }

try { echo

inverse(5) . "\n";
    echo inverse(0) . "\n";
} catch (Exception $e) {
    echo 'Caught exception: ',  $e->getMessage(), "\n";
}// Continue execution
echo "Hello World\n";
?>