Changes to error and exception handling

Many fatal and recoverable fatal errors have been converted to exceptions in PHP 7. These error exceptions inherit from the Error class, which itself implements the Throwable interface (the new base interface all exceptions inherit).

This means that custom error handlers may no longer be triggered because exceptions may be thrown instead (causing new fatal errors for uncaught Error exceptions).

A fuller description of how errors operate in PHP 7 can be found on the PHP 7 errors page. This migration guide will merely enumerate the changes that affect backward compatibility.

set_exception_handler() is no longer guaranteed to receive Exception objects

Code that implements an exception handler registered with set_exception_handler() using a type declaration of Exception will cause a fatal error when an Error object is thrown.

If the handler needs to work on both PHP 5 and 7, you should remove the type declaration from the handler, while code that is being migrated to work on PHP 7 exclusively can simply replace the Exception type declaration with Throwable instead.

<?php
// PHP 5 era code that will break.
function handler(Exception $e) { /* ... */ }
set_exception_handler('handler');

// PHP 5 and 7 compatible.
function handler($e) { /* ... */ }

// PHP 7 only.
function handler(Throwable $e) { /* ... */ }
?>

Internal constructors always throw exceptions on failure

Previously, some internal classes would return null or an unusable object when the constructor failed. All internal classes will now throw an Exception in this case in the same way that user classes already had to.

Parse errors throw ParseError

Parser errors now throw a ParseError object. Error handling for eval() should now include a Catch block that can handle this error.

E_STRICT notices severity changes

All of the E_STRICT notices have been reclassified to other levels. E_STRICT constant is retained, so calls like error_reporting(E_ALL|E_STRICT) will not cause an error.