Source of: /manual/en/functions.anonymous.php
<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.functions.inc";
$setup = array (
'home' =>
array (
0 => 'index.php',
1 => 'PHP Manual',
),
'head' =>
array (
0 => 'UTF-8',
1 => 'en',
),
'this' =>
array (
0 => 'functions.anonymous.php',
1 => 'Anonymous functions',
),
'up' =>
array (
0 => 'language.functions.php',
1 => 'Functions',
),
'prev' =>
array (
0 => 'functions.internal.php',
1 => 'Internal (built-in) functions',
),
'next' =>
array (
0 => 'language.oop5.php',
1 => 'Classes and Objects',
),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);
manual_header();
?>
<div id="functions.anonymous" class="sect1">
<h2 class="title">Anonymous functions</h2>
<p class="simpara">
Anonymous functions, also known as <i>closures</i>, allow the
creation of functions which have no specified name. They are most useful as
the value of <a href="language.pseudo-types.php#language.types.callback" class="link">callback</a>
parameters, but they have many other uses.
</p>
<div class="example">
<p><b>Example #1 Anonymous function example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">preg_replace_callback</span><span style="color: #007700">(</span><span style="color: #DD0000">'~-([a-z])~'</span><span style="color: #007700">, function (</span><span style="color: #0000BB">$match</span><span style="color: #007700">) {<br /> return </span><span style="color: #0000BB">strtoupper</span><span style="color: #007700">(</span><span style="color: #0000BB">$match</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">]);<br />}, </span><span style="color: #DD0000">'hello-world'</span><span style="color: #007700">);<br /></span><span style="color: #FF8000">// outputs helloWorld<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="simpara">
Closures can also be used as the values of variables; PHP automatically
converts such expressions into instances of the
<b class="classname">Closure</b> internal class. Assigning a closure to a
variable uses the same syntax as any other assignment, including the
trailing semicolon:
</p>
<div class="example">
<p><b>Example #2 Anonymous function variable assignment example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$greet </span><span style="color: #007700">= function(</span><span style="color: #0000BB">$name</span><span style="color: #007700">)<br />{<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Hello %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$name</span><span style="color: #007700">);<br />};<br /><br /></span><span style="color: #0000BB">$greet</span><span style="color: #007700">(</span><span style="color: #DD0000">'World'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$greet</span><span style="color: #007700">(</span><span style="color: #DD0000">'PHP'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="simpara">
Closures may also inherit variables from the parent scope. Any such
variables must be declared in the function header. Inheriting variables from
the parent scope is <em class="emphasis">not</em> the same as using global
variables. Global variables exist in the global scope, which is the same no
matter what function is executing. The parent scope of a closure is the
function in which the closure was declared (not necessarily the function it
was called from). See the following example:
</p>
<div class="example">
<p><b>Example #3 Closures and scoping</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">// A basic shopping cart which contains a list of added products<br />// and the quantity of each product. Includes a method which<br />// calculates the total price of the items in the cart using a<br />// closure as a callback.<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">Cart<br /></span><span style="color: #007700">{<br /> const </span><span style="color: #0000BB">PRICE_BUTTER </span><span style="color: #007700">= </span><span style="color: #0000BB">1.00</span><span style="color: #007700">;<br /> const </span><span style="color: #0000BB">PRICE_MILK </span><span style="color: #007700">= </span><span style="color: #0000BB">3.00</span><span style="color: #007700">;<br /> const </span><span style="color: #0000BB">PRICE_EGGS </span><span style="color: #007700">= </span><span style="color: #0000BB">6.95</span><span style="color: #007700">;<br /><br /> protected </span><span style="color: #0000BB">$products </span><span style="color: #007700">= array();<br /> <br /> public function </span><span style="color: #0000BB">add</span><span style="color: #007700">(</span><span style="color: #0000BB">$product</span><span style="color: #007700">, </span><span style="color: #0000BB">$quantity</span><span style="color: #007700">)<br /> {<br /> </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">products</span><span style="color: #007700">[</span><span style="color: #0000BB">$product</span><span style="color: #007700">] = </span><span style="color: #0000BB">$quantity</span><span style="color: #007700">;<br /> }<br /> <br /> public function </span><span style="color: #0000BB">getQuantity</span><span style="color: #007700">(</span><span style="color: #0000BB">$product</span><span style="color: #007700">)<br /> {<br /> return isset(</span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">products</span><span style="color: #007700">[</span><span style="color: #0000BB">$product</span><span style="color: #007700">]) ? </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">products</span><span style="color: #007700">[</span><span style="color: #0000BB">$product</span><span style="color: #007700">] :<br /> </span><span style="color: #0000BB">FALSE</span><span style="color: #007700">;<br /> }<br /> <br /> public function </span><span style="color: #0000BB">getTotal</span><span style="color: #007700">(</span><span style="color: #0000BB">$tax</span><span style="color: #007700">)<br /> {<br /> </span><span style="color: #0000BB">$total </span><span style="color: #007700">= </span><span style="color: #0000BB">0.00</span><span style="color: #007700">;<br /> <br /> </span><span style="color: #0000BB">$callback </span><span style="color: #007700">=<br /> function (</span><span style="color: #0000BB">$quantity</span><span style="color: #007700">, </span><span style="color: #0000BB">$product</span><span style="color: #007700">) use (</span><span style="color: #0000BB">$tax</span><span style="color: #007700">, &</span><span style="color: #0000BB">$total</span><span style="color: #007700">)<br /> {<br /> </span><span style="color: #0000BB">$pricePerItem </span><span style="color: #007700">= </span><span style="color: #0000BB">constant</span><span style="color: #007700">(</span><span style="color: #0000BB">__CLASS__ </span><span style="color: #007700">. </span><span style="color: #DD0000">"::PRICE_" </span><span style="color: #007700">.<br /> </span><span style="color: #0000BB">strtoupper</span><span style="color: #007700">(</span><span style="color: #0000BB">$product</span><span style="color: #007700">));<br /> </span><span style="color: #0000BB">$total </span><span style="color: #007700">+= (</span><span style="color: #0000BB">$pricePerItem </span><span style="color: #007700">* </span><span style="color: #0000BB">$quantity</span><span style="color: #007700">) * (</span><span style="color: #0000BB">$tax </span><span style="color: #007700">+ </span><span style="color: #0000BB">1.0</span><span style="color: #007700">);<br /> };<br /> <br /> </span><span style="color: #0000BB">array_walk</span><span style="color: #007700">(</span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">products</span><span style="color: #007700">, </span><span style="color: #0000BB">$callback</span><span style="color: #007700">);<br /> return </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">$total</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">);;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$my_cart </span><span style="color: #007700">= new </span><span style="color: #0000BB">Cart</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Add some items to the cart<br /></span><span style="color: #0000BB">$my_cart</span><span style="color: #007700">-></span><span style="color: #0000BB">add</span><span style="color: #007700">(</span><span style="color: #DD0000">'butter'</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$my_cart</span><span style="color: #007700">-></span><span style="color: #0000BB">add</span><span style="color: #007700">(</span><span style="color: #DD0000">'milk'</span><span style="color: #007700">, </span><span style="color: #0000BB">3</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$my_cart</span><span style="color: #007700">-></span><span style="color: #0000BB">add</span><span style="color: #007700">(</span><span style="color: #DD0000">'eggs'</span><span style="color: #007700">, </span><span style="color: #0000BB">6</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Print the total with a 5% sales tax.<br /></span><span style="color: #007700">print </span><span style="color: #0000BB">$my_cart</span><span style="color: #007700">-></span><span style="color: #0000BB">getTotal</span><span style="color: #007700">(</span><span style="color: #0000BB">0.05</span><span style="color: #007700">) . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /></span><span style="color: #FF8000">// The result is 54.29<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="simpara">
Anonymous functions are currently implemented using the
<a href="reserved.classes.php#reserved.classes.closure" class="link">
<b class="classname">Closure</b></a> class. This is an implementation
detail and should not be relied upon.
</p>
<blockquote><p><b class="note">Note</b>:
<span class="simpara">
Anonymous functions are available since PHP 5.3.0.
</span>
</p></blockquote>
<blockquote><p><b class="note">Note</b>:
<span class="simpara">
It is possible to use <a href="function.func-num-args.php" class="function">func_num_args()</a>,
<a href="function.func-get-arg.php" class="function">func_get_arg()</a>, and <a href="function.func-get-args.php" class="function">func_get_args()</a>
from within a closure.
</span>
</p></blockquote>
</div><?php manual_footer(); ?>
