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<title>Name resolution rules</title>
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</div><hr /><div id="language.namespaces.rules" class="sect1">
<h2 class="title">Name resolution rules</h2>
<p class="verinfo">(PHP 5 >= 5.3.0, PHP 7)</p>
<p class="para">
For the purposes of these resolution rules, here are some important definitions:
<dl>
<strong class="title">Namespace name definitions</strong>
<dt>
Unqualified name</dt>
<dd>
<p class="para">
This is an identifier without a namespace separator, such as <em>Foo</em>
</p>
</dd>
<dt>
Qualified name</dt>
<dd>
<p class="para">
This is an identifier with a namespace separator, such as <em>Foo\Bar</em>
</p>
</dd>
<dt>
Fully qualified name</dt>
<dd>
<p class="para">
This is an identifier with a namespace separator that begins with a
namespace separator, such as <em>\Foo\Bar</em>. The namespace
<em>\Foo</em> is also a fully qualified name.
</p>
</dd>
<dt>
Relative name</dt>
<dd>
<p class="para">
This is an identifier starting with <em>namespace</em>, such as
<em>namespace\Foo\Bar</em>.
</p>
</dd>
</dl>
</p>
<p class="para">
Names are resolved following these resolution rules:
<ol type="1">
<li class="listitem">
<span class="simpara">
Fully qualified names always resolve to the name without leading namespace separator.
For instance <em>\A\B</em> resolves to <em>A\B</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
Relative names always resolve to the name with <em>namespace</em> replaced by
the current namespace. If the name occurs in the global namespace, the
<em>namespace\</em> prefix is stripped. For example <em>namespace\A</em>
inside namespace <em>X\Y</em> resolves to <em>X\Y\A</em>. The same name
inside the global namespace resolves to <em>A</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
For qualified names the first segment of the name is translated according to the current
class/namespace import table. For example, if the namespace <em>A\B\C</em> is
imported as <em>C</em>, the name <em>C\D\E</em> is translated to
<em>A\B\C\D\E</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
For qualified names, if no import rule applies, the current namespace is prepended to the
name. For example, the name <em>C\D\E</em> inside namespace <em>A\B</em>,
resolves to <em>A\B\C\D\E</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
For unqualified names, the name is translated according to the current import table for the
respective symbol type. This means that class-like names are translated according to the
class/namespace import table, function names according to the function import table and
constants according to the constant import table. For example, after
<em>use A\B\C;</em> a usage such as <em>new C()</em> resolves to the name
<em>A\B\C()</em>. Similarly, after <em>use function A\B\fn;</em> a usage
such as <em>fn()</em> resolves to the name <em>A\B\fn</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
For unqualified names, if no import rule applies and the name refers to a class-like symbol,
the current namespace is prepended. For example <em>new C()</em> inside namespace
<em>A\B</em> resolves to name <em>A\B\C</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
For unqualified names, if no import rule applies and the name refers to a function or constant
and the code is outside the global namespace, the name is resolved at runtime.
Assuming the code is in namespace <em>A\B</em>, here is how a call to function
<em>foo()</em> is resolved:
</span>
<ol type="1">
<li class="listitem">
<span class="simpara">
It looks for a function from the current namespace:
<em>A\B\foo()</em>.
</span>
</li>
<li class="listitem">
<span class="simpara">
It tries to find and call the <em class="emphasis">global</em> function
<em>foo()</em>.
</span>
</li>
</ol>
</li>
</ol>
</p>
<div class="example" id="example-266">
<p><strong>Example #1 Name resolutions illustrated</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">;<br />use </span><span style="color: #0000BB">B</span><span style="color: #007700">\</span><span style="color: #0000BB">D</span><span style="color: #007700">, </span><span style="color: #0000BB">C</span><span style="color: #007700">\</span><span style="color: #0000BB">E </span><span style="color: #007700">as </span><span style="color: #0000BB">F</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// function calls<br /><br /></span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// first tries to call "foo" defined in namespace "A"<br /> // then calls global function "foo"<br /><br /></span><span style="color: #007700">\</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls function "foo" defined in global scope<br /><br /></span><span style="color: #0000BB">my</span><span style="color: #007700">\</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls function "foo" defined in namespace "A\my"<br /><br /></span><span style="color: #0000BB">F</span><span style="color: #007700">(); </span><span style="color: #FF8000">// first tries to call "F" defined in namespace "A"<br /> // then calls global function "F"<br /><br />// class references<br /><br /></span><span style="color: #007700">new </span><span style="color: #0000BB">B</span><span style="color: #007700">(); </span><span style="color: #FF8000">// creates object of class "B" defined in namespace "A"<br /> // if not found, it tries to autoload class "A\B"<br /><br /></span><span style="color: #007700">new </span><span style="color: #0000BB">D</span><span style="color: #007700">(); </span><span style="color: #FF8000">// using import rules, creates object of class "D" defined in namespace "B"<br /> // if not found, it tries to autoload class "B\D"<br /><br /></span><span style="color: #007700">new </span><span style="color: #0000BB">F</span><span style="color: #007700">(); </span><span style="color: #FF8000">// using import rules, creates object of class "E" defined in namespace "C"<br /> // if not found, it tries to autoload class "C\E"<br /><br /></span><span style="color: #007700">new \</span><span style="color: #0000BB">B</span><span style="color: #007700">(); </span><span style="color: #FF8000">// creates object of class "B" defined in global scope<br /> // if not found, it tries to autoload class "B"<br /><br /></span><span style="color: #007700">new \</span><span style="color: #0000BB">D</span><span style="color: #007700">(); </span><span style="color: #FF8000">// creates object of class "D" defined in global scope<br /> // if not found, it tries to autoload class "D"<br /><br /></span><span style="color: #007700">new \</span><span style="color: #0000BB">F</span><span style="color: #007700">(); </span><span style="color: #FF8000">// creates object of class "F" defined in global scope<br /> // if not found, it tries to autoload class "F"<br /><br />// static methods/namespace functions from another namespace<br /><br /></span><span style="color: #0000BB">B</span><span style="color: #007700">\</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls function "foo" from namespace "A\B"<br /><br /></span><span style="color: #0000BB">B</span><span style="color: #007700">::</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls method "foo" of class "B" defined in namespace "A"<br /> // if class "A\B" not found, it tries to autoload class "A\B"<br /><br /></span><span style="color: #0000BB">D</span><span style="color: #007700">::</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// using import rules, calls method "foo" of class "D" defined in namespace "B"<br /> // if class "B\D" not found, it tries to autoload class "B\D"<br /><br /></span><span style="color: #007700">\</span><span style="color: #0000BB">B</span><span style="color: #007700">\</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls function "foo" from namespace "B"<br /><br /></span><span style="color: #007700">\</span><span style="color: #0000BB">B</span><span style="color: #007700">::</span><span style="color: #0000BB">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls method "foo" of class "B" from global scope<br /> // if class "B" not found, it tries to autoload class "B"<br /><br />// static methods/namespace functions of current namespace<br /><br /></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">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls method "foo" of class "B" from namespace "A\A"<br /> // if class "A\A\B" not found, it tries to autoload class "A\A\B"<br /><br /></span><span style="color: #007700">\</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">foo</span><span style="color: #007700">(); </span><span style="color: #FF8000">// calls method "foo" of class "B" from namespace "A"<br /> // if class "A\B" not found, it tries to autoload class "A\B"<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
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