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https://github.com/php/doc-zh.git
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mowangjuanzi
319 lines
7.1 KiB
XML
319 lines
7.1 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: 8bf3587d8f70239a65d9aa44d42ced8a696a3e86 Maintainer: 邹松 Status: ready -->
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<!-- CREDITS: mowangjuanzi -->
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<refentry xml:id="function.array-column" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>array_column</refname>
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<refpurpose>返回输入数组中指定列的值</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type>array</type><methodname>array_column</methodname>
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<methodparam><type>array</type><parameter>array</parameter></methodparam>
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<methodparam><type class="union"><type>int</type><type>string</type><type>null</type></type><parameter>column_key</parameter></methodparam>
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<methodparam choice="opt"><type class="union"><type>int</type><type>string</type><type>null</type></type><parameter>index_key</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<para>
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<function>array_column</function> 返回
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<parameter>array</parameter> 中键名为
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<parameter>column_key</parameter> 的一列值。 如果指定了可选参数
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<parameter>index_key</parameter>，则使用输入数组中
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<parameter>index_key</parameter> 列的值将作为返回数组中对应值的键。
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>array</parameter></term>
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<listitem>
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<para>
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多维数组或对象数组，从中提取一列值。
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如果提供的是对象数组，只有 public 的属性会被直接取出。
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如果想取出 private 和 protected 的属性，类必须实现
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<function>__get</function> 和 <function>__isset</function> 魔术方法。
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>column_key</parameter></term>
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<listitem>
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<para>
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需要返回值的列。它可以是索引数组的列索引，或者是关联数组的列的键，也可以是属性名。
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也可以是 &null; ，此时将返回整个数组（配合
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<parameter>index_key</parameter> 参数来重新索引数组时非常好用）。
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>index_key</parameter></term>
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<listitem>
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<para>
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作为返回数组的索引/键的列。它可以是该列的整数索引，或者字符串键值。
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该值会像数组键一样被 <link linkend="language.types.array.key-casts">强制转换</link>
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（但是，在 PHP 8.0.0 之前，也被允许支持转换为字符串对象）。
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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返回输入数组中单列值的数组。
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</para>
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<para>
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>8.0.0</entry>
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<entry>
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<parameter>index_key</parameter> 参数指定的列中的对象不再强制转换为字符串，而是会抛出
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<classname>TypeError</classname>。
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</para>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title>从结果集中取出 first_name 列</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// 表示从数据库返回的记录集的数组
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$records = [
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[
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'id' => 2135,
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'first_name' => 'John',
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'last_name' => 'Doe',
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],
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[
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'id' => 3245,
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'first_name' => 'Sally',
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'last_name' => 'Smith',
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],
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[
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'id' => 5342,
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'first_name' => 'Jane',
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'last_name' => 'Jones',
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],
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[
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'id' => 5623,
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'first_name' => 'Peter',
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'last_name' => 'Doe',
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]
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];
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$first_names = array_column($records, 'first_name');
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print_r($first_names);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Array
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(
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[0] => John
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[1] => Sally
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[2] => Jane
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[3] => Peter
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)
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>
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从结果集中总取出 last_name 列，用相应的“id”作为键值
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</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// 使用示例 #1 中的 $records 数组
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$records = [
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[
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'id' => 2135,
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'first_name' => 'John',
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'last_name' => 'Doe',
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],
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[
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'id' => 3245,
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'first_name' => 'Sally',
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'last_name' => 'Smith',
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],
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[
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'id' => 5342,
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'first_name' => 'Jane',
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'last_name' => 'Jones',
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],
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[
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'id' => 5623,
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'first_name' => 'Peter',
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'last_name' => 'Doe',
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]
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];
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$last_names = array_column($records, 'last_name', 'id');
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print_r($last_names);
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Array
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(
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[2135] => Doe
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[3245] => Smith
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[5342] => Jones
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[5623] => Doe
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)
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>
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username 列是从对象获取 public 的 "username" 属性
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</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class User
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{
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public $username;
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public function __construct(string $username)
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{
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$this->username = $username;
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}
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}
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$users = [
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new User('user 1'),
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new User('user 2'),
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new User('user 3'),
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];
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print_r(array_column($users, 'username'));
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Array
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(
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[0] => user 1
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[1] => user 2
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[2] => user 3
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)
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example>
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<title>
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通过 <function>__isset</function> 和 <function>__get</function> 魔术方法从对象中获取 private 属性的 "name" 列。
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</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class Person
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{
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private $name;
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public function __construct(string $name)
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{
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$this->name = $name;
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}
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public function __get($prop)
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{
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return $this->$prop;
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}
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public function __isset($prop) : bool
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{
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return isset($this->$prop);
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}
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}
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$people = [
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new Person('Fred'),
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new Person('Jane'),
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new Person('John'),
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];
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print_r(array_column($people, 'name'));
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen role="php">
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<![CDATA[
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Array
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(
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[0] => Fred
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[1] => Jane
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[2] => John
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)
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]]>
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</screen>
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</example>
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如果不提供 <function>__isset</function>，会返回空数组。
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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