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<refentry xml:id="function.print-r" xmlns="http://docbook.org/ns/docbook">

<refnamediv>

<refname>print_r</refname>

<refpurpose>

打印人类可读的变量信息

</refpurpose>

</refnamediv>

<refsect1 role="description">

&reftitle.description;

<methodsynopsis>

<type class="union"><type>string</type><type>true</type></type><methodname>print_r</methodname>

<methodparam><type>mixed</type><parameter>value</parameter></methodparam>

<methodparam choice="opt"><type>bool</type><parameter>return</parameter><initializer>&false;</initializer></methodparam>

</methodsynopsis>

<para>

<function>print_r</function> 以人类可读的方式显示变量的信息。

</para>

<para>

<function>print_r</function>、<function>var_dump</function>、<function>var_export</function>

还将显示对象的 protected 和 private 属性。不会显示静态类成员。

</para>

</refsect1>

<refsect1 role="parameters">

&reftitle.parameters;

<para>

<variablelist>

<varlistentry>

<term><parameter>value</parameter></term>

<listitem>

<para>

要打印的表达式。

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>return</parameter></term>

<listitem>

<para>

想要捕获 <function>print_r</function> 的输出，请使用 <parameter>return</parameter>

参数。当此参数为 &true;，<function>print_r</function> 将返回信息，而不是打印它。

</para>

</listitem>

</varlistentry>

</variablelist>

</para>

</refsect1>

<refsect1 role="returnvalues">

&reftitle.returnvalues;

<para>

如果是指定 <type>string</type>、<type>int</type> 或 <type>float</type>，会直接打印值本身。如果是指定

<type>array</type>，值将以键和元素的格式显示。<type>object</type> 也一样。

</para>

<para>

当 <parameter>return</parameter> 参数设置成 &true;，本函数会返回 <type>string</type>。否则返回 &true;。

</para>

</refsect1>

<refsect1 role="changelog">

&reftitle.changelog;

<para>

<informaltable>

<tgroup cols="2">

<thead>

<row>

<entry>&Version;</entry>

<entry>&Description;</entry>

</row>

</thead>

<tbody>

<row>

<entry>8.4.0</entry>

<entry>

返回类型从 <type class="union"><type>string</type><type>bool</type></type> 变为 <type class="union"><type>string</type><type>true</type></type>。

</entry>

</row>

</tbody>

</tgroup>

</informaltable>

</para>

</refsect1>

<refsect1 role="examples">

&reftitle.examples;

<para>

<example>

<title><function>print_r</function> 示例</title>

<programlisting role="php">

<![CDATA[

<pre>

<?php

$a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x', 'y', 'z'));

print_r ($a);

?>

</pre>

]]>

</programlisting>

&example.outputs;

<screen>

<![CDATA[

<pre>

Array

(

[a] => apple

[b] => banana

[c] => Array

(

[0] => x

[1] => y

[2] => z

)

)

</pre>

]]>

</screen>

</example>

</para>

<para>

<example>

<title><parameter>return</parameter> 参数的例子</title>

<programlisting role="php">

<![CDATA[

<?php

$b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z'));

$results = print_r($b, true); // $results 包含了 print_r 的输出

?>

]]>

</programlisting>

</example>

</para>

</refsect1>

<refsect1 role="notes">

&reftitle.notes;

&note.uses-ob-php70;

</refsect1>

<refsect1 role="seealso">

&reftitle.seealso;

<para>

<simplelist>

<member><function>ob_start</function></member>

<member><function>var_dump</function></member>

<member><function>var_export</function></member>

</simplelist>

</para>

</refsect1>

</refentry>

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