Source of: /manual/en/migration53.incompatible.php
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<div id="migration53.incompatible" class="section">
<h2 class="title">Backward Incompatible Changes</h2>
<p class="simpara">
Although most existing PHP 5 code should work without changes, please take
note of some backward incompatible changes:
</p>
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
The newer internal parameter parsing API has been applied across all the
extensions bundled with PHP 5.3.x. This parameter parsing API causes
functions to return <b><tt class="constant">NULL</tt></b> when passed incompatible parameters. There are
some exceptions to this rule, such as the <a href="function.get-class.php" class="function">get_class()</a>
function, which will continue to return <b><tt class="constant">FALSE</tt></b> on error.
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="function.clearstatcache.php" class="function">clearstatcache()</a> no longer clears the realpath cache by
default.
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="function.realpath.php" class="function">realpath()</a> is now fully platform-independent.
</span>
</li>
<li class="listitem">
<span class="simpara">
The <a href="function.call-user-func.php" class="function">call_user_func()</a> family of functions now propagate
<i>$this</i> even if the callee is a parent class.
</span>
</li>
<li class="listitem">
<span class="simpara">
The array functions <a href="function.natsort.php" class="function">natsort()</a>,
<a href="function.natcasesort.php" class="function">natcasesort()</a>, <a href="function.usort.php" class="function">usort()</a>,
<a href="function.uasort.php" class="function">uasort()</a>, <a href="function.uksort.php" class="function">uksort()</a>,
<a href="function.array-flip.php" class="function">array_flip()</a>, and <a href="function.array-unique.php" class="function">array_unique()</a> no
longer accept objects passed as arguments. To apply these functions to an
object, cast the object to an array first.
</span>
</li>
<li class="listitem">
<span class="simpara">
The behaviour of functions with by-reference parameters called by value has
changed. Where previously the function would accept the by-value argument,
a fatal error is now emitted. Any previous code passing constants or
literals to functions expecting references, will need altering to assign
the value to a variable before calling the function.
</span>
</li>
<li class="listitem">
<span class="simpara">
The new mysqlnd library necessitates the use of MySQL 4.1's newer 41-byte
password format. Continued use of the old 16-byte passwords will cause
<a href="function.mysql-connect.php" class="function">mysql_connect()</a> and similar functions to emit the error,
<i>"mysqlnd cannot connect to MySQL 4.1+ using old
authentication."</i>
</span>
</li>
<li class="listitem">
<span class="simpara">
The new mysqlnd library does not read mysql configuration files
(my.cnf/my.ini), as the older libmysql library does. If your code relies on
settings in the configuration file, you can load it explicitly with the
<a href="mysqli.options.php" class="function">mysqli_options()</a> function.
</span>
</li>
<li class="listitem">
<span class="simpara">
The trailing / has been removed from the <a href="class.splfileinfo.php" class="classname">SplFileInfo</a>
class and other related directory classes.
</span>
</li>
<li class="listitem">
<span class="simpara">
The <a href="language.oop5.magic.php#language.oop5.magic.tostring" class="link">__toString</a> magic
method can no longer accept arguments.
</span>
</li>
<li class="listitem">
<span class="simpara">
The magic methods
<a href="language.oop5.overloading.php#language.oop5.overloading.members" class="link">__get</a>,
<a href="language.oop5.overloading.php#language.oop5.overloading.members" class="link">__set</a>,
<a href="language.oop5.overloading.php#language.oop5.overloading.members" class="link">__isset</a>,
<a href="language.oop5.overloading.php#language.oop5.overloading.members" class="link">__unset</a>, and
<a href="language.oop5.overloading.php#language.oop5.overloading.methods" class="link">__call</a> must always
be public and can no longer be static. Method signatures are now enforced.
</span>
</li>
<li class="listitem">
<span class="simpara">
The <a href="language.oop5.overloading.php#language.oop5.overloading.methods" class="link">__call</a>
magic method is now invoked on access to private and protected methods.
</span>
</li>
</ul>
<p class="simpara">
The following keywords are now reserved and may not be used in function,
class, etc. names.
</p>
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
<a href="control-structures.goto.php" class="link">goto</a>
</span>
</li>
<li class="listitem">
<span class="simpara">
<a href="language.namespaces.php" class="link">namespace</a>
</span>
</li>
</ul>
</div><?php manual_footer(); ?>
