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魔王卷子
265 lines
6.5 KiB
XML
Executable File
265 lines
6.5 KiB
XML
Executable File
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: 3ef3e56c80f7ae6b6a7291b7eb57dc6250b50801 Maintainer: daijie Status: ready -->
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<refentry xml:id="function.count" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>count</refname>
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<refpurpose>统计数组、<interfacename>Countable</interfacename> 对象中所有元素的数量</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>int</type><methodname>count</methodname>
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<methodparam><type class="union"><type>Countable</type><type>array</type></type><parameter>value</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>mode</parameter><initializer><constant>COUNT_NORMAL</constant></initializer></methodparam>
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</methodsynopsis>
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<para>
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用于数组时，统计数组中元素的数量；用于实现了 <interfacename>Countable</interfacename>
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接口的对象时，返回 <methodname>Countable::count</methodname> 方法的返回值。
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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>value</parameter></term>
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<listitem>
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<para>
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数组或者 <interfacename>Countable</interfacename> 对象。
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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>mode</parameter></term>
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<listitem>
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<para>
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如果可选的 <parameter>mode</parameter> 参数设为
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<constant>COUNT_RECURSIVE</constant>（或 1），<function>count</function>
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将递归地对数组计数。对计算多维数组的所有单元尤其有用。
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</para>
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<caution>
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<para>
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<function>count</function> 能检测递归来避免无限循环，但每次出现时会产生 <constant>E_WARNING</constant> 错误
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（如果 array 不止一次包含了自身）并返回大于预期的统计数字。
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</para>
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</caution>
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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 <parameter>value</parameter> 中的元素的数量。在 PHP 8.0.0
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之前，如果参数既不是数组也不是实现了 <literal>Countable</literal> 接口的对象，将返回
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<literal>1</literal>。当 <parameter>value</parameter> 为 &null; 时返回
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<literal>0</literal>。
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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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<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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当 <parameter>value</parameter> 参数传入了无效的 countable 类型，
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<function>count</function> 现在会抛出 <classname>TypeError</classname>。
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</entry>
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</row>
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<row>
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<entry>7.2.0</entry>
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<entry>
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当 <parameter>value</parameter> 参数传入了无效的 countable 类型，
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<function>count</function> 现在会产生警告。
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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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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example xml:id="count.example.basic">
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<title><function>count</function> 例子</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$a[0] = 1;
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$a[1] = 3;
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$a[2] = 5;
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var_dump(count($a));
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$b[0] = 7;
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$b[5] = 9;
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$b[10] = 11;
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var_dump(count($b));
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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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int(3)
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int(3)
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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 xml:id="count.example.badexample">
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<title><function>count</function> 非 Countable|array 的例子 （这是个反例，请勿模仿）</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$b[0] = 7;
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$b[5] = 9;
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$b[10] = 11;
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var_dump(count($b));
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var_dump(count(null));
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var_dump(count(false));
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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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int(3)
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int(0)
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int(1)
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]]>
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</screen>
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&example.outputs.72;
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<screen role="php">
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<![CDATA[
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int(3)
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Warning: count(): Parameter must be an array or an object that implements Countable in … on line 12
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int(0)
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Warning: count(): Parameter must be an array or an object that implements Countable in … on line 14
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int(1)
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]]>
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</screen>
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&example.outputs.8;
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<screen role="php">
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<![CDATA[
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int(3)
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Fatal error: Uncaught TypeError: count(): Argument #1 ($var) must be of type Countable .. on line 12
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]]>
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</screen>
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</example>
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</para>
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<para>
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<example xml:id="count.example.recursive">
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<title>递归 <function>count</function> 例子</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$food = array('fruits' => array('orange', 'banana', 'apple'),
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'veggie' => array('carrot', 'collard', 'pea'));
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// 递归计数
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var_dump(count($food, COUNT_RECURSIVE));
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// 常规计数
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var_dump(count($food));
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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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int(8)
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int(2)
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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 xml:id="count.example.countable">
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<title><interfacename>Countable</interfacename> 对象</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class CountOfMethods implements Countable
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{
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private function someMethod()
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{
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}
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public function count(): int
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{
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return count(get_class_methods($this));
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}
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}
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$obj = new CountOfMethods();
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var_dump(count($obj));
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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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int(2)
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]]>
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</screen>
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</example>
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</para>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>is_array</function></member>
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<member><function>isset</function></member>
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<member><function>empty</function></member>
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<member><function>strlen</function></member>
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<member><function>is_countable</function></member>
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<member><link linkend="language.types.array">Array 数组</link></member>
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</simplelist>
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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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