<!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>Anonymous functions</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="functions.internal.html">Internal (built-in) functions</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.oop5.html">Classes and Objects</a></div> <div class="up"><a href="language.functions.html">Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="functions.anonymous" class="sect1"> <h2 class="title">Anonymous functions</h2> <p class="simpara"> Anonymous functions, also known as <em>closures</em>, allow the creation of functions which have no specified name. They are most useful as the value of <a href="language.pseudo-types.html#language.types.callback" class="link">callback</a> parameters, but they have many other uses. </p> <p class="simpara"> Anonymous functions are implemented using the <a href="class.closure.html" class="link"> <a href="class.closure.html" class="classname">Closure</a></a> class. </p> <div class="example" id="example-163"> <p><strong>Example #1 Anonymous function example</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">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 <a href="class.closure.html" class="classname">Closure</a> internal class. Assigning a closure to a variable uses the same syntax as any other assignment, including the trailing semicolon: </p> <div class="example" id="example-164"> <p><strong>Example #2 Anonymous function variable assignment example</strong></p> <div class="example-contents"> <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">$greet</span><span style="color: #007700">(</span><span style="color: #DD0000">'PHP'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> </div> <p class="simpara"> Closures may also inherit variables from the parent scope. Any such variables must be passed to the <em>use</em> language construct. From PHP 7.1, these variables must not include <a href="language.variables.predefined.html" class="link">superglobals</a>, <var class="varname"><var class="varname">$this</var></var>, or variables with the same name as a parameter. </p> <div class="example" id="example-165"> <p><strong>Example #3 Inheriting variables from the parent scope</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br />$message </span><span style="color: #007700">= </span><span style="color: #DD0000">'hello'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// No "use"<br /></span><span style="color: #0000BB">$example </span><span style="color: #007700">= function () {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$message</span><span style="color: #007700">);<br />};<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// Inherit $message<br /></span><span style="color: #0000BB">$example </span><span style="color: #007700">= function () use (</span><span style="color: #0000BB">$message</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$message</span><span style="color: #007700">);<br />};<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// Inherited variable's value is from when the function<br />// is defined, not when called<br /></span><span style="color: #0000BB">$message </span><span style="color: #007700">= </span><span style="color: #DD0000">'world'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// Reset message<br /></span><span style="color: #0000BB">$message </span><span style="color: #007700">= </span><span style="color: #DD0000">'hello'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// Inherit by-reference<br /></span><span style="color: #0000BB">$example </span><span style="color: #007700">= function () use (&</span><span style="color: #0000BB">$message</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$message</span><span style="color: #007700">);<br />};<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// The changed value in the parent scope<br />// is reflected inside the function call<br /></span><span style="color: #0000BB">$message </span><span style="color: #007700">= </span><span style="color: #DD0000">'world'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">// Closures can also accept regular arguments<br /></span><span style="color: #0000BB">$example </span><span style="color: #007700">= function (</span><span style="color: #0000BB">$arg</span><span style="color: #007700">) use (</span><span style="color: #0000BB">$message</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$arg </span><span style="color: #007700">. </span><span style="color: #DD0000">' ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$message</span><span style="color: #007700">);<br />};<br /></span><span style="color: #0000BB">$example</span><span style="color: #007700">(</span><span style="color: #DD0000">"hello"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output something similar to:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> Notice: Undefined variable: message in /example.php on line 6 NULL string(5) "hello" string(5) "hello" string(5) "hello" string(5) "world" string(11) "hello world" </pre></div> </div> </div> <p class="simpara"> 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" id="example-166"> <p><strong>Example #4 Closures and scoping</strong></p> <div class="example-contents"> <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> <div class="example" id="example-167"> <p><strong>Example #5 Automatic binding of <em>$this</em></strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">class </span><span style="color: #0000BB">Test<br /></span><span style="color: #007700">{<br /> public function </span><span style="color: #0000BB">testing</span><span style="color: #007700">()<br /> {<br /> return function() {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$this</span><span style="color: #007700">);<br /> };<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$object </span><span style="color: #007700">= new </span><span style="color: #0000BB">Test</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$function </span><span style="color: #007700">= </span><span style="color: #0000BB">$object</span><span style="color: #007700">-></span><span style="color: #0000BB">testing</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">$function</span><span style="color: #007700">();<br /> <br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> object(Test)#1 (0) { } </pre></div> </div> <div class="example-contents"><p>Output of the above example in PHP 5.3:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> Notice: Undefined variable: this in script.php on line 8 NULL</pre></div> </div> </div> <p class="para"> As of PHP 5.4.0, when declared in the context of a class, the current class is automatically bound to it, making <em>$this</em> available inside of the function's scope. If this automatic binding of the current class is not wanted, then <a href="functions.anonymous.html#functions.anonymous-functions.static" class="link">static anonymous functions</a> may be used instead. </p> <div class="sect2" id="functions.anonymous-functions.static"> <h3 class="title">Static anonymous functions</h3> <p class="para"> As of PHP 5.4, anonymous functions may be declared statically. This prevents them from having the current class automatically bound to them. Objects may also not be bound to them at runtime. </p> <p class="para"> <div class="example" id="example-168"> <p><strong>Example #6 Attempting to use <em>$this</em> inside a static anonymous function</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br /></span><span style="color: #007700">class </span><span style="color: #0000BB">Foo<br /></span><span style="color: #007700">{<br /> function </span><span style="color: #0000BB">__construct</span><span style="color: #007700">()<br /> {<br /> </span><span style="color: #0000BB">$func </span><span style="color: #007700">= static function() {<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$this</span><span style="color: #007700">);<br /> };<br /> </span><span style="color: #0000BB">$func</span><span style="color: #007700">();<br /> }<br />};<br />new </span><span style="color: #0000BB">Foo</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> Notice: Undefined variable: this in %s on line %d NULL </pre></div> </div> </div> </p> <p class="para"> <div class="example" id="example-169"> <p><strong>Example #7 Attempting to bind an object to a static anonymous function</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br /><br />$func </span><span style="color: #007700">= static function() {<br /> </span><span style="color: #FF8000">// function body<br /></span><span style="color: #007700">};<br /></span><span style="color: #0000BB">$func </span><span style="color: #007700">= </span><span style="color: #0000BB">$func</span><span style="color: #007700">-></span><span style="color: #0000BB">bindTo</span><span style="color: #007700">(new </span><span style="color: #0000BB">StdClass</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$func</span><span style="color: #007700">();<br /><br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> <div class="example-contents"><p>The above example will output:</p></div> <div class="example-contents screen"> <div class="cdata"><pre> Warning: Cannot bind an instance to a static closure in %s on line %d </pre></div> </div> </div> </p> </div> <div class="sect2"> <h3 class="title">Changelog</h3> <p class="para"> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>7.1.0</td> <td> Anonymous functions may not close over <a href="language.variables.predefined.html" class="link">superglobals</a>, <var class="varname"><var class="varname">$this</var></var>, or any variable with the same name as a parameter. </td> </tr> <tr> <td>5.4.0</td> <td> Anonymous functions may use <var class="varname"><var class="varname">$this</var></var>, as well as be declared statically. </td> </tr> <tr> <td>5.3.0</td> <td> Anonymous functions become available. </td> </tr> </tbody> </table> </p> </div> <div class="sect2"> <h3 class="title">Notes</h3> <blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara"> It is possible to use <span class="function"><a href="function.func-num-args.html" class="function">func_num_args()</a></span>, <span class="function"><a href="function.func-get-arg.html" class="function">func_get_arg()</a></span>, and <span class="function"><a href="function.func-get-args.html" class="function">func_get_args()</a></span> from within a closure. </span> </p></blockquote> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="functions.internal.html">Internal (built-in) functions</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.oop5.html">Classes and Objects</a></div> <div class="up"><a href="language.functions.html">Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div></body></html>