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Using PHP Error Handling
Throwing errors from PHP pages
Throwing errors from a PHP page is quite the same as emulating Apache's behaviour for ErrorDocument
directives, you simply redirect the user using a query-string that specifies variables that
Apache usually sets as environment variables. This makes it possible to use the same error page
for all kinds of errors. An example:
<?php
function throw_error($message) {
$error_page = "/err/error.php";
$error_url = $error_page;
$error_url .= "?REDIRECT_ERROR_NOTES=$message";
$error_url .= "&REDIRECT_URL=" . $GLOBALS["PHP_SELF"];
$error_url .= "&REDIRECT_REQUEST_METHOD=$REQUEST_METHOD";
$error_url .= "&REDIRECT_STATUS=501";
Header("Status: 501");
Header("Location: $error_url");
exit;
}
ob_start(); // Use output buffering to be able to throw errors anywhere on this page.
if(!condition) {
throw_error("the condition failed");
}
ob_end_flush(); // Page rendered, flush the output buffer.
?>
Using the PHP4 feature called output buffering also helps creating generic error reporting
functionality. By not flushing the output buffer until you are sure the whole page has rendered
error-free, you are able to make Header calls anywhere in your code to redirect the user.
I'll leave up to the reader to design and implement his/her own error.php page to suit his/her site.
Don't forget that you can include a form with email submission possibilities for the users to send
you comments.
