silverstripe-framework/core/startup/ErrorControlChain.php

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<?php
/**
* Class ErrorControlChain
*
* Runs a set of steps, optionally suppressing (but recording) any errors (even fatal ones) that occur in each step.
* If an error does occur, subsequent steps are normally skipped, but can optionally be run anyway
*
* Normal errors are suppressed even past the end of the chain. Fatal errors are only suppressed until the end
* of the chain - the request will then die silently.
*
* The exception is if an error occurs and BASE_URL is not yet set - in that case the error is never suppressed.
*
* Usage:
*
* $chain = new ErrorControlChain();
* $chain->then($callback1)->then($callback2)->then(true, $callback3)->execute();
*
* WARNING: This class is experimental and designed specifically for use pre-startup in main.php
* It will likely be heavily refactored before the release of 3.2
*/
class ErrorControlChain {
protected $error = false;
protected $steps = array();
protected $suppression = true;
/** We can't unregister_shutdown_function, so this acts as a flag to enable handling */
protected $handleFatalErrors = false;
public function hasErrored() {
return $this->error;
}
public function setErrored($error) {
$this->error = (bool)$error;
}
public function setSuppression($suppression) {
$this->suppression = (bool)$suppression;
}
/**
* Add this callback to the chain of callbacks to call along with the state
* that $error must be in this point in the chain for the callback to be called
*
* @param $callback - The callback to call
* @param $onErrorState - false if only call if no errors yet, true if only call if already errors, null for either
* @return $this
*/
public function then($callback, $onErrorState = false) {
$this->steps[] = array(
'callback' => $callback,
'onErrorState' => $onErrorState
);
return $this;
}
public function thenWhileGood($callback) {
return $this->then($callback, false);
}
public function thenIfErrored($callback) {
return $this->then($callback, true);
}
public function thenAlways($callback) {
return $this->then($callback, null);
}
public function handleError() {
if ($this->suppression && defined('BASE_URL')) throw new Exception('Generic Error');
else return false;
}
protected function lastErrorWasFatal() {
$error = error_get_last();
return $error && $error['type'] == 1;
}
public function handleFatalError() {
if ($this->handleFatalErrors && $this->suppression && defined('BASE_URL')) {
if ($this->lastErrorWasFatal()) {
ob_clean();
$this->error = true;
$this->step();
}
}
}
public function execute() {
set_error_handler(array($this, 'handleError'), error_reporting());
register_shutdown_function(array($this, 'handleFatalError'));
$this->handleFatalErrors = true;
$this->step();
}
protected function step() {
if ($this->steps) {
$step = array_shift($this->steps);
if ($step['onErrorState'] === null || $step['onErrorState'] === $this->error) {
try {
call_user_func($step['callback'], $this);
}
catch (Exception $e) {
if ($this->suppression && defined('BASE_URL')) $this->error = true;
else throw $e;
}
}
$this->step();
}
else {
// Now clean up
$this->handleFatalErrors = false;
restore_error_handler();
}
}
}