language.pseudo-types.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Pseudo-types and variables used in this documentation</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.types.null.html">NULL</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.types.type-juggling.html">Type Juggling</a></div> <div class="up"><a href="language.types.html">Types</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.pseudo-types" class="sect1"> <h2 class="title">Pseudo-types and variables used in this documentation</h2> <div id="language.types.mixed" class="sect2"> <h3 class="title">mixed</h3> <p class="para"> <i>mixed</i> indicates that a parameter may accept multiple (but not necessarily all) types. </p> <p class="para"> <a href="function.gettype.html" class="function">gettype()</a> for example will accept all PHP types, while <a href="function.str-replace.html" class="function">str_replace()</a> will accept <a href="language.types.string.html" class="type string">string</a>s and <a href="language.types.array.html" class="type array">array</a>s. </p> </div> <div id="language.types.number" class="sect2"> <h3 class="title">number</h3> <p class="para"> <i>number</i> indicates that a parameter can be either <a href="language.types.integer.html" class="type integer">integer</a> or <a href="language.types.float.html" class="type float">float</a>. </p> </div> <div id="language.types.callback" class="sect2"> <h3 class="title">callback</h3> <p class="para"> Some functions like <a href="function.call-user-func.html" class="function">call_user_func()</a> or <a href="function.usort.html" class="function">usort()</a> accept user-defined callback functions as a parameter. Callback functions can not only be simple functions, but also <a href="language.types.object.html" class="type object">object</a> methods, including static class methods. </p> <p class="para"> A PHP function is passed by its name as a <a href="language.types.string.html" class="type string">string</a>. Any built-in or user-defined function can be used, except language constructs such as: <a href="function.array.html" class="function">array()</a>, <a href="function.echo.html" class="function">echo()</a>, <a href="function.empty.html" class="function">empty()</a>, <a href="function.eval.html" class="function">eval()</a>, <a href="function.exit.html" class="function">exit()</a>, <a href="function.isset.html" class="function">isset()</a>, <a href="function.list.html" class="function">list()</a>, <a href="function.print.html" class="function">print()</a> or <a href="function.unset.html" class="function">unset()</a>. </p> <p class="para"> A method of an instantiated <a href="language.types.object.html" class="type object">object</a> is passed as an <a href="language.types.array.html" class="type array">array</a> containing an <a href="language.types.object.html" class="type object">object</a> at index 0 and the method name at index 1. </p> <p class="para"> Static class methods can also be passed without instantiating an <a href="language.types.object.html" class="type object">object</a> of that class by passing the class name instead of an <a href="language.types.object.html" class="type object">object</a> at index 0. </p> <p class="para"> Apart from common user-defined function, <a href="function.create-function.html" class="function">create_function()</a> can also be used to create an anonymous callback function. </p> <div class="example"> <p><b>Example #1 Callback function examples </b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php <br /><br /></span><span style="color: #FF8000">// An example callback function<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">my_callback_function</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">'hello world!'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #FF8000">// An example callback method<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">MyClass </span><span style="color: #007700">{<br /> static function </span><span style="color: #0000BB">myCallbackMethod</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">'Hello World!'</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #FF8000">// Type 1: Simple callback<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #DD0000">'my_callback_function'</span><span style="color: #007700">); <br /><br /></span><span style="color: #FF8000">// Type 2: Static class method call<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'MyClass'</span><span style="color: #007700">, </span><span style="color: #DD0000">'myCallbackMethod'</span><span style="color: #007700">)); <br /><br /></span><span style="color: #FF8000">// Type 3: Object method call<br /></span><span style="color: #0000BB">$obj </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">, </span><span style="color: #DD0000">'myCallbackMethod'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// Type 4: Static class method call (As of PHP 5.2.3)<br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(</span><span style="color: #DD0000">'MyClass::myCallbackMethod'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// Type 5: Relative static class method call (As of PHP 5.3.0)<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public static function </span><span style="color: #0000BB">who</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">"A\n"</span><span style="color: #007700">;<br /> }<br />}<br /><br />class </span><span style="color: #0000BB">B </span><span style="color: #007700">extends </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public static function </span><span style="color: #0000BB">who</span><span style="color: #007700">() {<br /> echo </span><span style="color: #DD0000">"B\n"</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">call_user_func</span><span style="color: #007700">(array(</span><span style="color: #DD0000">'B'</span><span style="color: #007700">, </span><span style="color: #DD0000">'parent::who'</span><span style="color: #007700">)); </span><span style="color: #FF8000">// A<br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div> <blockquote><p><b class="note">Note</b>: <span class="simpara"> In PHP4, it was necessary to use a reference to create a callback that points to the actual <a href="language.types.object.html" class="type object">object</a>, and not a copy of it. For more details, see <a href="language.references.html" class="link">References Explained</a>. </span> </p></blockquote> </div> <div id="language.types.void" class="sect2"> <h3 class="title">void</h3> <p class="para"> <i>void</i> as a return type means that the return value is useless. <i>void</i> in a parameter list means that the function doesn't accept any parameters. </p> </div> <div id="language.types.dotdotdot" class="sect2"> <h3 class="title">...</h3> <p class="para"> <i><tt class="parameter">$...</tt></i> in function prototypes means <i>and so on</i>. This variable name is used when a function can take an endless number of arguments. </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.types.null.html">NULL</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.types.type-juggling.html">Type Juggling</a></div> <div class="up"><a href="language.types.html">Types</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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