Php как правильно обработать ошибку 404

<?phpif (!function_exists('http_response_code')) {
        function http_response_code($code = NULL) {

            if (

$code !== NULL) {

                switch (

$code) {
                    case 100: $text = 'Continue'; break;
                    case 101: $text = 'Switching Protocols'; break;
                    case 200: $text = 'OK'; break;
                    case 201: $text = 'Created'; break;
                    case 202: $text = 'Accepted'; break;
                    case 203: $text = 'Non-Authoritative Information'; break;
                    case 204: $text = 'No Content'; break;
                    case 205: $text = 'Reset Content'; break;
                    case 206: $text = 'Partial Content'; break;
                    case 300: $text = 'Multiple Choices'; break;
                    case 301: $text = 'Moved Permanently'; break;
                    case 302: $text = 'Moved Temporarily'; break;
                    case 303: $text = 'See Other'; break;
                    case 304: $text = 'Not Modified'; break;
                    case 305: $text = 'Use Proxy'; break;
                    case 400: $text = 'Bad Request'; break;
                    case 401: $text = 'Unauthorized'; break;
                    case 402: $text = 'Payment Required'; break;
                    case 403: $text = 'Forbidden'; break;
                    case 404: $text = 'Not Found'; break;
                    case 405: $text = 'Method Not Allowed'; break;
                    case 406: $text = 'Not Acceptable'; break;
                    case 407: $text = 'Proxy Authentication Required'; break;
                    case 408: $text = 'Request Time-out'; break;
                    case 409: $text = 'Conflict'; break;
                    case 410: $text = 'Gone'; break;
                    case 411: $text = 'Length Required'; break;
                    case 412: $text = 'Precondition Failed'; break;
                    case 413: $text = 'Request Entity Too Large'; break;
                    case 414: $text = 'Request-URI Too Large'; break;
                    case 415: $text = 'Unsupported Media Type'; break;
                    case 500: $text = 'Internal Server Error'; break;
                    case 501: $text = 'Not Implemented'; break;
                    case 502: $text = 'Bad Gateway'; break;
                    case 503: $text = 'Service Unavailable'; break;
                    case 504: $text = 'Gateway Time-out'; break;
                    case 505: $text = 'HTTP Version not supported'; break;
                    default:
                        exit('Unknown http status code "' . htmlentities($code) . '"');
                    break;
                }$protocol = (isset($_SERVER['SERVER_PROTOCOL']) ? $_SERVER['SERVER_PROTOCOL'] : 'HTTP/1.0');header($protocol . ' ' . $code . ' ' . $text);$GLOBALS['http_response_code'] = $code;

            } else {

$code = (isset($GLOBALS['http_response_code']) ? $GLOBALS['http_response_code'] : 200);

            }

            return

$code;

        }
    }

?>

In this example I am using $GLOBALS, but you can use whatever storage mechanism you like... I don't think there is a way to return the current status code:

https://bugs.php.net/bug.php?id=52555

For reference the error codes I got from PHP's source code:

http://lxr.php.net/opengrok/xref/PHP_5_4/sapi/cgi/cgi_main.c#354

And how the current http header is sent, with the variables it uses:

http://lxr.php.net/opengrok/xref/PHP_5_4/main/SAPI.c#856

The following codes currently work as expected (with PHP running as Apache module):
200 – 208, 226
300 – 305, 307, 308
400 – 417, 422 – 424, 426, 428 – 429, 431
500 – 508, 510 – 511

Codes 0, 100, 101, and 102 will be sent as "200 OK".

Everything else will result in "500 Internal Server Error".

If you want to send responses with a freestyle status line, you need to use the `header()` function:

<?php header("HTTP/1.0 418 I'm A Teapot"); ?>

This happens when using header(0,0,420) and http_response_code(420).
Use header('HTTP/1.1 420 Enhance Your Calm') instead.

Note that the response code in the string IS interpreted and used in the access log and output via http_response_code().

<?php
$http_status_codes = array(100 => "Continue", 101 => "Switching Protocols", 102 => "Processing", 200 => "OK", 201 => "Created", 202 => "Accepted", 203 => "Non-Authoritative Information", 204 => "No Content", 205 => "Reset Content", 206 => "Partial Content", 207 => "Multi-Status", 300 => "Multiple Choices", 301 => "Moved Permanently", 302 => "Found", 303 => "See Other", 304 => "Not Modified", 305 => "Use Proxy", 306 => "(Unused)", 307 => "Temporary Redirect", 308 => "Permanent Redirect", 400 => "Bad Request", 401 => "Unauthorized", 402 => "Payment Required", 403 => "Forbidden", 404 => "Not Found", 405 => "Method Not Allowed", 406 => "Not Acceptable", 407 => "Proxy Authentication Required", 408 => "Request Timeout", 409 => "Conflict", 410 => "Gone", 411 => "Length Required", 412 => "Precondition Failed", 413 => "Request Entity Too Large", 414 => "Request-URI Too Long", 415 => "Unsupported Media Type", 416 => "Requested Range Not Satisfiable", 417 => "Expectation Failed", 418 => "I'm a teapot", 419 => "Authentication Timeout", 420 => "Enhance Your Calm", 422 => "Unprocessable Entity", 423 => "Locked", 424 => "Failed Dependency", 424 => "Method Failure", 425 => "Unordered Collection", 426 => "Upgrade Required", 428 => "Precondition Required", 429 => "Too Many Requests", 431 => "Request Header Fields Too Large", 444 => "No Response", 449 => "Retry With", 450 => "Blocked by Windows Parental Controls", 451 => "Unavailable For Legal Reasons", 494 => "Request Header Too Large", 495 => "Cert Error", 496 => "No Cert", 497 => "HTTP to HTTPS", 499 => "Client Closed Request", 500 => "Internal Server Error", 501 => "Not Implemented", 502 => "Bad Gateway", 503 => "Service Unavailable", 504 => "Gateway Timeout", 505 => "HTTP Version Not Supported", 506 => "Variant Also Negotiates", 507 => "Insufficient Storage", 508 => "Loop Detected", 509 => "Bandwidth Limit Exceeded", 510 => "Not Extended", 511 => "Network Authentication Required", 598 => "Network read timeout error", 599 => "Network connect timeout error");
?>

Source: Wikipedia "List_of_HTTP_status_codes"

<?php
header('HTTP/1.1 401 Unauthorized');
http_response_code(403);
print(http_response_code());
?>

The raw HTTP response will be (notice the actual status code on the first line does not match the printed http_response_code in the body):

HTTP/1.1 401 Unauthorized
Date: Tue, 24 Nov 2020 13:49:08 GMT
Server: Apache
Connection: Upgrade, Keep-Alive
Keep-Alive: timeout=5, max=100
Transfer-Encoding: chunked
Content-Type: text/html; charset=UTF-8

403

I only tested it on Apache. I am not sure if this behavior is specific to Apache or common to all PHP distributions.

        const

<?php
header($_SERVER['SERVER_PROTOCOL'] . ' 507 Insufficient Storage');
?>
result: something like

HTTP/1.1 507 Insufficient Storage

The documentation for the header() function has the right way to implement this if you're still on < php 5.4:

<?php
header("HTTP/1.0 404 Not Found");
?>

In summary - The differences between "http_response_code" and "header" for setting response codes:

1. Using http_response_code will cause PHP to match and apply a Reason Phrase from a list of Reason Phrases that are hard-coded into the PHP source code.

2. Because of point 1 above, if you use http_response_code you must set a code that PHP knows about. You can't set your own custom code, however you can set a custom code (and Reason Phrase) if you use the header method.

<?php// HTTP/1.1 404 Not Found
http_response_code(404);?>

The resulting response is HTTP/1.1 404 OK

$a

<?php

header

('Temporary-Header: True', true, 404);
header_remove('Temporary-Header');?>

if (!function_exists('http_response_code')) {
    function http_response_code($code = NULL) {    
        $prev_code = (isset($GLOBALS['http_response_code']) ? $GLOBALS['http_response_code'] : 200);

        if ($code === NULL) {
            return $prev_code;
        }

        switch ($code) {
            case 100: $text = 'Continue'; break;
            case 101: $text = 'Switching Protocols'; break;
            case 200: $text = 'OK'; break;
            case 201: $text = 'Created'; break;
            case 202: $text = 'Accepted'; break;
            case 203: $text = 'Non-Authoritative Information'; break;
            case 204: $text = 'No Content'; break;
            case 205: $text = 'Reset Content'; break;
            case 206: $text = 'Partial Content'; break;
            case 300: $text = 'Multiple Choices'; break;
            case 301: $text = 'Moved Permanently'; break;
            case 302: $text = 'Moved Temporarily'; break;
            case 303: $text = 'See Other'; break;
            case 304: $text = 'Not Modified'; break;
            case 305: $text = 'Use Proxy'; break;
            case 400: $text = 'Bad Request'; break;
            case 401: $text = 'Unauthorized'; break;
            case 402: $text = 'Payment Required'; break;
            case 403: $text = 'Forbidden'; break;
            case 404: $text = 'Not Found'; break;
            case 405: $text = 'Method Not Allowed'; break;
            case 406: $text = 'Not Acceptable'; break;
            case 407: $text = 'Proxy Authentication Required'; break;
            case 408: $text = 'Request Time-out'; break;
            case 409: $text = 'Conflict'; break;
            case 410: $text = 'Gone'; break;
            case 411: $text = 'Length Required'; break;
            case 412: $text = 'Precondition Failed'; break;
            case 413: $text = 'Request Entity Too Large'; break;
            case 414: $text = 'Request-URI Too Large'; break;
            case 415: $text = 'Unsupported Media Type'; break;
            case 500: $text = 'Internal Server Error'; break;
            case 501: $text = 'Not Implemented'; break;
            case 502: $text = 'Bad Gateway'; break;
            case 503: $text = 'Service Unavailable'; break;
            case 504: $text = 'Gateway Time-out'; break;
            case 505: $text = 'HTTP Version not supported'; break;
            default:
                trigger_error('Unknown http status code ' . $code, E_USER_ERROR); // exit('Unknown http status code "' . htmlentities($code) . '"');
                return $prev_code;
        }

        $protocol = (isset($_SERVER['SERVER_PROTOCOL']) ? $_SERVER['SERVER_PROTOCOL'] : 'HTTP/1.0');
        header($protocol . ' ' . $code . ' ' . $text);
        $GLOBALS['http_response_code'] = $code;

        // original function always returns the previous or current code
        return $prev_code;
    }
}

Test code:
<php
http_response_code(500);  // set the code
var_dump(headers_sent());  // check if headers are sent
http_response_code(200);  // avoid a default browser page

<?php

header

('Status: 404', TRUE, 404);?>

you might wanna do something like
function ehttp_response_code(int $response_code = NULL): int {
    if ($response_code === NULL) {
        return http_response_code();
    }
    if (headers_sent()) {
        throw new Exception('tried to change http response code after sending headers!');
    }
    return http_response_code($response_code);
}