<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Using namespaces: fallback to global function/constant</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="language.namespaces.global.html">Global space</a></div>
<div class="next" style="text-align: right; float: right;"><a href="language.namespaces.rules.html">Name resolution rules</a></div>
<div class="up"><a href="language.namespaces.html">Namespaces</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="language.namespaces.fallback" class="sect1">
<h2 class="title">Using namespaces: fallback to global function/constant</h2>
<p class="verinfo">(PHP 5 >= 5.3.0)</p>
<p class="para">
Inside a namespace, when PHP encounters an unqualified Name in a class name, function or
constant context, it resolves these with different priorities. Class names always
resolve to the current namespace name. Thus to access internal or non-namespaced
user classes, one must refer to them with their fully qualified Name as in:
<div class="example" id="example-255">
<p><strong>Example #1 Accessing global classes inside a namespace</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">namespace </span><span style="color: #0000BB">A</span><span style="color: #007700">\</span><span style="color: #0000BB">B</span><span style="color: #007700">\</span><span style="color: #0000BB">C</span><span style="color: #007700">;<br />class </span><span style="color: #0000BB">Exception </span><span style="color: #007700">extends \</span><span style="color: #0000BB">Exception </span><span style="color: #007700">{}<br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">Exception</span><span style="color: #007700">(</span><span style="color: #DD0000">'hi'</span><span style="color: #007700">); </span><span style="color: #FF8000">// $a is an object of class A\B\C\Exception<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= new \</span><span style="color: #0000BB">Exception</span><span style="color: #007700">(</span><span style="color: #DD0000">'hi'</span><span style="color: #007700">); </span><span style="color: #FF8000">// $b is an object of class Exception<br /><br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= new </span><span style="color: #0000BB">ArrayObject</span><span style="color: #007700">; </span><span style="color: #FF8000">// fatal error, class A\B\C\ArrayObject not found<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
<p class="para">
For functions and constants, PHP will fall back to global functions or constants
if a namespaced function or constant does not exist.
<div class="example" id="example-256">
<p><strong>Example #2 global functions/constants fallback inside a namespace</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">namespace </span><span style="color: #0000BB">A</span><span style="color: #007700">\</span><span style="color: #0000BB">B</span><span style="color: #007700">\</span><span style="color: #0000BB">C</span><span style="color: #007700">;<br /><br />const </span><span style="color: #0000BB">E_ERROR </span><span style="color: #007700">= </span><span style="color: #0000BB">45</span><span style="color: #007700">;<br />function </span><span style="color: #0000BB">strlen</span><span style="color: #007700">(</span><span style="color: #0000BB">$str</span><span style="color: #007700">)<br />{<br /> return \</span><span style="color: #0000BB">strlen</span><span style="color: #007700">(</span><span style="color: #0000BB">$str</span><span style="color: #007700">) - </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />}<br /><br />echo </span><span style="color: #0000BB">E_ERROR</span><span style="color: #007700">, </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">; </span><span style="color: #FF8000">// prints "45"<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">INI_ALL</span><span style="color: #007700">, </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">; </span><span style="color: #FF8000">// prints "7" - falls back to global INI_ALL<br /><br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">strlen</span><span style="color: #007700">(</span><span style="color: #DD0000">'hi'</span><span style="color: #007700">), </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">; </span><span style="color: #FF8000">// prints "1"<br /></span><span style="color: #007700">if (</span><span style="color: #0000BB">is_array</span><span style="color: #007700">(</span><span style="color: #DD0000">'hi'</span><span style="color: #007700">)) { </span><span style="color: #FF8000">// prints "is not array"<br /> </span><span style="color: #007700">echo </span><span style="color: #DD0000">"is array\n"</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">"is not array\n"</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="language.namespaces.global.html">Global space</a></div>
<div class="next" style="text-align: right; float: right;"><a href="language.namespaces.rules.html">Name resolution rules</a></div>
<div class="up"><a href="language.namespaces.html">Namespaces</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
