Logging Symfony deprecation errors to the log

DeprecationErrorHandler.php

/**
 * The goal of this handler is to write all silenced (@) E_USER_DEPRECATION
 * errors to the server error log.
 *
 * Please note that only one error handler can be active at any given point in
 * time. This means two things:
 * - We have to be a good citizen and call the previous error handler (if any).
 * - We're fully dependant for later error handlers to do the same thing.
 */
class DeprecationErrorHandler
{
    private $previous_handler;

    public function __construct()
    {
        $this->previous_handler = set_error_handler([$this, 'handleError']);
    }

    /**
     * Logs silenced (error_reporting = 0) E_USER_DEPRECATED errors, and
     * forwards to other error handler.
     *
     * @param int $errno
     * @param string $errstr
     * @param string $errfile
     * @param int $errline
     * @param array $errcontext
     */
    public function handleError($errno, $errstr, $errfile = null, $errline = null, array $errcontext = [])
    {
        // Suppressing AsseticBundle v2.7.1 since it spams errors.
        // See https://github.com/symfony/assetic-bundle/pull/395
        if ($errno === E_USER_DEPRECATED
            && error_reporting() === 0
            && strpos($errstr, 'AsseticBundle') === false
        ) {
            error_log(sprintf('PHP Deprecated: %s in %s on line %d', $errstr, $errfile, $errline), 0);
        }

        // Always attempt to call the previous handler
        if (is_callable($this->previous_handler)) {
            return call_user_func($this->previous_handler, $errno, $errstr, $errfile, $errline, $errcontext);
        }
        // Returning false indicates we did not handle the error, so normal handling should continue.
        return false;
    }
}
new DeprecationErrorHandler();