[PHP-NOTES] note 130185 added to function.set-error-handler

While on this doc/page about PHP's "set_error_handler()", the reader needs to definitely be made aware of "set_exception_handler()", so I am trying to provide that benefit with this post along with a good/simple model to utilize for global error/exception-handling for a page/app that smartly routes how the page/app responds to errors and exceptions.

<?php

//Below code is written in a PHP 8.3 context.

error_reporting(E_ALL); //<--can restrict further/later as desired/needed.

ini_set('display_errors', '1'); /* <--Yes, do display errors so can understand what goes wrong prior to getting throwable-handling set up. Once your
Throwable-handling is in place, you control what gets displayed despite this setting. */

$in_dev_mode = true; //<--global var to help illustrate implementation.

/* Below function is the "global/catch-all" handler of Errors/Exceptions which all originate from class Throwable. */
function my_initial_exception_handler(Throwable $ref_throwable):never{
    $err_num = $ref_throwable->getCode();
    $err_msg = $ref_throwable->getMessage();
    $file_path = $ref_throwable->getFile();
    $line_num = $ref_throwable->getLine();

    //Log the error regardless of whether in dev-mode...
    $str_for_logger = "err_msg='{$err_msg}'; file_path='{$file_path}'; err_num='{$err_num}'; line_num='{$line_num}'";
    error_log($str_for_logger, 3, "/path/to/error.log");

    //But selectively control what goes to screen...
    global $in_dev_mode;
    if($in_dev_mode===true){
        $str_display_to_browser = <<<GHUJ87TGH
        <div style="color: red; font-size: x-large;">
            err_msg='{$err_msg}'
            <br>
            file_path='{$file_path}'
            <br>
            err_num='{$err_num}'
            <br>
            line_num='{$line_num}'
        </div>
GHUJ87TGH;
    }else{
        $str_display_to_browser = 'Sorry, but an error/exception occurred.';
    }

    echo $str_display_to_browser;
    exit;
} //end fn

set_exception_handler('my_initial_exception_handler');

/*
--Internal PHP functions mainly use Error reporting, while only modern Object-oriented extensions use exceptions.
  But...reported-errors can be converted to exceptions using class 'ErrorException' (the technique only works with non-fatal errors).
--Recall also that the fn registered using 'set_error_handler()' gets called when fn trigger_error() is called in PHP code,
  making it essential to have the below 'set_error_handler()' registration and error-reporting conversion in-place.
*/
set_error_handler(
    function($severity, $message, $file, $line){
        //The below "@noinspection" directive/annotation is optional and spares you from IDE warnings:
        /** @noinspection PhpUnhandledExceptionInspection */
        throw new ErrorException($message, 0, $severity, $file, $line);
    }
);

/*
...and below is where your php page/app begins its work...

Once you get your auto-loading set up, or your require() calls in-place to bring in your custom classes, you can call function "set_exception_handler()" again to switch over to your better/more robust handler.
*/

echo 'Hello World and welcome to my amazing app.';
?>

Know also that if you are "raising errors" in your PHP code, you likely no longer want to do it using "trigger_error()"--but you of course can if you choose, and if you do, the code above handles getting things switch over to a thrown Exception. The new way is to use the newer technique of using:
"throw new Exception('error message goes here.');". And do not forget, one may benefit from extending the Exception class with one's own custom Exception class and throwing it instead.
----
Server IP: 45.112.84.4
Probable Submitter: 45.112.84.18 (proxied: 96.60.59.42)
----
Manual Page -- https://php.net/manual/en/function.set-error-handler.php
Edit        -- https://main.php.net/note/edit/130185
Del: integrated  -- https://main.php.net/note/delete/130185/integrated
Del: useless     -- https://main.php.net/note/delete/130185/useless
Del: bad code    -- https://main.php.net/note/delete/130185/bad+code
Del: spam        -- https://main.php.net/note/delete/130185/spam
Del: non-english -- https://main.php.net/note/delete/130185/non-english
Del: in docs     -- https://main.php.net/note/delete/130185/in+docs
Del: other reasons-- https://main.php.net/note/delete/130185
Reject      -- https://main.php.net/note/reject/130185
Search      -- https://main.php.net/manage/user-notes.php