set_error_handler()¶
set_error_handler() is a native PHP function, which replaces the default error handler from PHP with a custom one.
set_error_handler() is often used for custom logging, user-friendly or user-facing error messages, and debugging with extra details.
set_error_handler() takes a custom function, or closure, that is called upon encountering a triggered error: such errors are raised by code execution, or trigger manually with trigger_error().
set_error_handler() takes list of handled type of errors: for example, E_WARNING configures the custom handler to be called only for warnings. All other errors will be passed to the PHP default handler. In other words, each successive call of set_error_handler() replaces the preceding one.
The callback in set_error_handler() must terminate the script, with exit, if needed. When that callback returns, the code execution continues.
The callback in set_error_handler() returns a boolean. When it returns true, the warning is supposed to be handled, and PHP won’t process it further. When it returns false, the warning is also processed by PHP, on top of the custom handler: in particular, the error message will be displayed, according to configuration.
set_error_handler() does not handle Error, such as fatal error: they must be execution errors.
set_error_handler() does not handle Exception, which are handled by try-catch-finally structures.
set_error_handler() may be reverted to default with restore_error_handler().
<?php
function myHandler(
int $errno,
string $errstr,
string $errfile = '',
int $errline = 0,
array $errcontext = array()
): bool {
print 'A warning was detected: '.$errstr;
return true;
}
set_error_handler(myHandler(...), E_USER_WARNING);
trigger_error('hello!', E_USER_WARNING);
// PHP only
trigger_error('World!', E_USER_NOTICE);
?>
Related : Try-catch, trigger_error(), Exception, PHP Handlers, Exit, display_errors, Error Reporting
