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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<sect2 xml:id="migration70.incompatible.error-handling">
<title>Changes to error and exception handling</title>
<para>
Many fatal and recoverable fatal errors have been converted to exceptions in
PHP 7. These error exceptions inherit from the <classname>Error</classname>
class, which itself implements the <classname>Throwable</classname>
interface (the new base interface all exceptions inherit).
</para>
<para>
This means that custom error handlers may no longer be triggered because
exceptions may be thrown instead (causing new fatal errors for uncaught
<classname>Error</classname> exceptions).
</para>
<para>
A fuller description of how errors operate in PHP 7 can be found
<link linkend="language.errors.php7">on the PHP 7 errors page</link>. This
migration guide will merely enumerate the changes that affect backward
compatibility.
</para>
<sect3 xml:id="migration70.incompatible.error-handling.set-exception-handler">
<title>
<function>set_exception_handler</function> is no longer guaranteed to
receive <classname>Exception</classname> objects
</title>
<para>
Code that implements an exception handler registered with
<function>set_exception_handler</function> using a type declaration of
<classname>Exception</classname> will cause a fatal error when an
<classname>Error</classname> object is thrown.
</para>
<para>
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
<classname>Exception</classname> type declaration with
<classname>Throwable</classname> instead.
</para>
<informalexample>
<programlisting role="php">
<![CDATA[
<?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) { ... }
?>
]]>
</programlisting>
</informalexample>
</sect3>
<sect3 xml:id="migration70.incompatible.error-handling.constructors">
<title>Internal constructors always throw exceptions on failure</title>
<para>
Previously, some internal classes would return &null; or an unusable object
when the constructor failed. All internal classes will now throw an
<classname>Exception</classname> in this case in the same way that user
classes already had to.
</para>
</sect3>
<sect3 xml:id="migration70.incompatible.error-handling.parse">
<title>Parse errors throw <classname>ParseError</classname></title>
<para>
Parser errors now throw a <classname>ParseError</classname> object. Error
handling for <function>eval</function> should now include a &catch; block
that can handle this error.
</para>
</sect3>
<sect3 xml:id="migration70.incompatible.error-handling.strict">
<title>E_STRICT notices severity changes</title>
<para>
All of the <constant>E_STRICT</constant> notices have been reclassified to
other levels. <constant>E_STRICT</constant> constant is retained, so calls like
<literal>error_reporting(E_ALL|E_STRICT)</literal> will not cause an error.
</para>
<para>
<table>
<title><constant>E_STRICT</constant> notices severity changes</title>
<tgroup cols="2">
<thead>
<row>
<entry>Situation</entry>
<entry>New level/behaviour</entry>
</row>
</thead>
<tbody>
<row>
<entry>Indexing by a resource</entry>
<entry><constant>E_NOTICE</constant></entry>
</row>
<row>
<entry>Abstract static methods</entry>
<entry>Notice removed, triggers no error</entry>
</row>
<row>
<entry>"Redefining" a constructor</entry>
<entry>Notice removed, triggers no error</entry>
</row>
<row>
<entry>Signature mismatch during inheritance</entry>
<entry><constant>E_WARNING</constant></entry>
</row>
<row>
<entry>Same (compatible) property in two used traits</entry>
<entry>Notice removed, triggers no error</entry>
</row>
<row>
<entry>Accessing static property non-statically</entry>
<entry><constant>E_NOTICE</constant></entry>
</row>
<row>
<entry>Only variables should be assigned by reference</entry>
<entry><constant>E_NOTICE</constant></entry>
</row>
<row>
<entry>Only variables should be passed by reference</entry>
<entry><constant>E_NOTICE</constant></entry>
</row>
<row>
<entry>Calling non-static methods statically</entry>
<entry><constant>E_DEPRECATED</constant></entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</sect3>
</sect2>
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