svn: /phpdoc/de/trunk/language/ functions.xml

cmb                                      Mon, 27 Apr 2020 07:16:30 +0000

Revision: http://svn.php.net/viewvc?view=revision&revision=349712

Log:
Fix build

Changed paths:
    U   phpdoc/de/trunk/language/functions.xml

Modified: phpdoc/de/trunk/language/functions.xml
===================================================================
--- phpdoc/de/trunk/language/functions.xml	2020-04-27 06:59:43 UTC (rev 349711)
+++ phpdoc/de/trunk/language/functions.xml	2020-04-27 07:16:30 UTC (rev 349712)
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!-- $Revision$ -->
-<!-- EN-Revision: 347269 Maintainer: cmb Status: ready -->
+<!-- EN-Revision: 347269 Maintainer: cmb Status: in progress -->
 <!-- Credits: hholzgra, tom, updated to fix build by theseer -->

  <chapter xml:id="language.functions" xmlns="http://docbook.org/ns/docbook">
@@ -1770,6 +1770,171 @@

   </sect1>

+  <sect1 xml:id="functions.arrow">
+   <title>Arrow Functions</title>
+
+   <simpara>
+    Arrow functions were introduced in PHP 7.4 as a more concise syntax for
+    <link linkend="functions.anonymous">anonymous functions</link>.
+   </simpara>
+   <simpara>
+    Both anonymous functions and arrow functions are implemented using the
+    <link linkend="class.closure"><classname>Closure</classname></link> class.
+   </simpara>
+
+   <simpara>
+    Arrow functions have the basic form
+    <code>fn (argument_list) =&gt; expr</code>.
+   </simpara>
+
+   <simpara>
+    Arrow functions support the same features as
+    <link linkend="functions.anonymous">anonymous functions</link>,
+    except that using variables from the parent scope is always automatic.
+   </simpara>
+
+   <simpara>
+    When a variable used in the expression is defined in the parent scope
+    it will be implicitly captured by-value.
+    In the following example, the functions <varname>$fn1</varname> and
+    <varname>$fn2</varname> behave the same way.
+   </simpara>
+
+   <para>
+    <example>
+     <title>Arrow functions capture variables by value automatically</title>
+     <programlisting role="php">
+<![CDATA[
+<?php
+
+$y = 1;
+
+$fn1 = fn($x) => $x + $y;
+// equivalent to using $y by value:
+$fn2 = function ($x) use ($y) {
+    return $x + $y;
+};
+
+var_export($fn1(3));
+?>
+]]>
+     </programlisting>
+     &example.outputs;
+     <screen>
+<![CDATA[
+4
+]]>
+      </screen>
+    </example>
+   </para>
+   <simpara>
+    This also works if the arrow functions are nested:
+   </simpara>
+   <para>
+    <example>
+     <title>Arrow functions capture variables by value automatically, even when nested</title>
+     <programlisting role="php">
+<![CDATA[
+<?php
+
+$z = 1;
+$fn = fn($x) => fn($y) => $x * $y + $z;
+// Outputs 51
+var_export($fn(5)(10));
+?>
+]]>
+     </programlisting>
+    </example>
+   </para>
+   <simpara>
+    Similarly to anonymous functions,
+    the arrow function syntax allows arbitrary function signatures,
+    including parameter and return types, default values, variadics,
+    as well as by-reference passing and returning.
+    All of the following are valid examples of arrow functions:
+   </simpara>
+   <para>
+    <example>
+     <title>Examples of arrow functions</title>
+     <programlisting role="php">
+<![CDATA[
+<?php
+
+fn(array $x) => $x;
+static fn(): int => $x;
+fn($x = 42) => $x;
+fn(&$x) => $x;
+fn&($x) => $x;
+fn($x, ...$rest) => $rest;
+
+?>
+]]>
+     </programlisting>
+    </example>
+   </para>
+   <simpara>
+    Arrow functions use by-value variable binding.
+    This is roughly equivalent to performing a <code>use($x)</code> for every
+    variable <varname>$x</varname> used inside the arrow function.
+    A by-value binding means that it is not possible to modify any values
+    from the outer scope.
+    <link linkend="functions.anonymous">Anonymous functions</link>
+    can be used instead for by-ref bindings.
+   </simpara>
+   <para>
+    <example>
+     <title>Values from the outer scope cannot be modified by arrow functions</title>
+     <programlisting role="php">
+<![CDATA[
+<?php
+
+$x = 1;
+$fn = fn() => $x++; // Has no effect
+$fn();
+var_export($x);  // Outputs 1
+
+?>
+]]>
+     </programlisting>
+    </example>
+   </para>
+
+   <sect2 role="changelog">
+    &reftitle.changelog;
+    <para>
+     <informaltable>
+      <tgroup cols="2">
+       <thead>
+        <row>
+         <entry>&Version;</entry>
+         <entry>&Description;</entry>
+        </row>
+       </thead>
+       <tbody>
+        <row>
+         <entry>7.4.0</entry>
+         <entry>
+          Arrow functions became available.
+         </entry>
+        </row>
+       </tbody>
+      </tgroup>
+     </informaltable>
+    </para>
+   </sect2>
+
+   <sect2 role="notes">
+    &reftitle.notes;
+    <note>
+     <simpara>
+      It is possible to use <function>func_num_args</function>,
+      <function>func_get_arg</function>, and <function>func_get_args</function>
+      from within an arrow function.
+     </simpara>
+    </note>
+   </sect2>
+  </sect1>
+
  </chapter>

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