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156 lines
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156 lines
14 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>输出一个或多个字符串</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.echo" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">echo</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">echo</span> — <span class="dc-title">输出一个或多个字符串</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.echo-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>echo</strong></span>
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( <span class="methodparam"><span class="type">string</span> <code class="parameter">$arg1</code></span>
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[, <span class="methodparam"><span class="type">string</span> <code class="parameter">$...</code></span>
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] ) : <span class="type"><span class="type void">void</span></span></div>
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<p class="simpara">
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输出所有参数。不会换行。
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</p>
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<p class="para">
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<span class="function"><strong>echo</strong></span> 不是一个函数（它是一个语言结构），
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因此你不一定要使用小括号来指明参数，单引号，双引号都可以。
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<span class="function"><strong>echo</strong></span> （不像其他语言构造）不表现得像一个函数，
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所以不能总是使用一个函数的上下文。 另外，如果你想给<span class="function"><strong>echo</strong></span>
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传递多个参数， 那么就不能使用小括号。
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</p>
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<p class="para">
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<span class="function"><strong>echo</strong></span> 也有一个快捷用法，你可以在打开标记前直接用一个等号。在 PHP 5.4.0 之前，必须在php.ini
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里面启用 <a href="ini.core.html#ini.short-open-tag" class="link">short_open_tag</a> 才有效。
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<div class="informalexample">
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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I have <span style="color: #0000BB"><?=$foo?></span> foo.</span>
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</pre></div>
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</div>
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</div>
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</p>
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<p class="para">
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和 <em>print</em> 最主要的不同之处是，
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<em>echo</em> 接受参数列表，并且没有返回值。
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.echo-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">arg1</code></dt>
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<dd>
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<p class="para">
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要输出的参数
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</p>
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</dd>
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<dt>
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<code class="parameter">...</code></dt>
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<dd>
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<p class="para">
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</p>
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</dd>
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</dl>
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</p>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.echo-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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没有返回值。
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.echo-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-5902">
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<p><strong>Example #1 <span class="function"><strong>echo</strong></span> 例子</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">"Hello World"</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #DD0000">"This spans<br />multiple lines. The newlines will be<br />output as well"</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #DD0000">"This spans\nmultiple lines. The newlines will be\noutput as well."</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #DD0000">"Escaping characters is done \"Like this\"."</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// You can use variables inside of an echo statement<br /></span><span style="color: #0000BB">$foo </span><span style="color: #007700">= </span><span style="color: #DD0000">"foobar"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$bar </span><span style="color: #007700">= </span><span style="color: #DD0000">"barbaz"</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #DD0000">"foo is </span><span style="color: #0000BB">$foo</span><span style="color: #DD0000">"</span><span style="color: #007700">; </span><span style="color: #FF8000">// foo is foobar<br /><br />// You can also use arrays<br /></span><span style="color: #0000BB">$baz </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"value" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"foo"</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #DD0000">"this is </span><span style="color: #007700">{</span><span style="color: #0000BB">$baz</span><span style="color: #007700">[</span><span style="color: #DD0000">'value'</span><span style="color: #007700">]}</span><span style="color: #DD0000"> !"</span><span style="color: #007700">; </span><span style="color: #FF8000">// this is foo !<br /><br />// Using single quotes will print the variable name, not the value<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'foo is $foo'</span><span style="color: #007700">; </span><span style="color: #FF8000">// foo is $foo<br /><br />// If you are not using any other characters, you can just echo variables<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$foo</span><span style="color: #007700">; </span><span style="color: #FF8000">// foobar<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$foo</span><span style="color: #007700">,</span><span style="color: #0000BB">$bar</span><span style="color: #007700">; </span><span style="color: #FF8000">// foobarbarbaz<br /><br />// Strings can either be passed individually as multiple arguments or<br />// concatenated together and passed as a single argument<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'This '</span><span style="color: #007700">, </span><span style="color: #DD0000">'string '</span><span style="color: #007700">, </span><span style="color: #DD0000">'was '</span><span style="color: #007700">, </span><span style="color: #DD0000">'made '</span><span style="color: #007700">, </span><span style="color: #DD0000">'with multiple parameters.'</span><span style="color: #007700">, </span><span style="color: #0000BB">chr</span><span style="color: #007700">(</span><span style="color: #0000BB">10</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">'This ' </span><span style="color: #007700">. </span><span style="color: #DD0000">'string ' </span><span style="color: #007700">. </span><span style="color: #DD0000">'was ' </span><span style="color: #007700">. </span><span style="color: #DD0000">'made ' </span><span style="color: #007700">. </span><span style="color: #DD0000">'with concatenation.' </span><span style="color: #007700">. </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br />echo <<<END<br /></span><span style="color: #DD0000">This uses the "here document" syntax to output<br />multiple lines with </span><span style="color: #0000BB">$variable</span><span style="color: #DD0000"> interpolation. Note<br />that the here document terminator must appear on a<br />line with just a semicolon. no extra whitespace!<br /></span><span style="color: #007700">END;<br /><br /></span><span style="color: #FF8000">// Because echo does not behave like a function, the following code is invalid.<br /></span><span style="color: #007700">(</span><span style="color: #0000BB">$some_var</span><span style="color: #007700">) ? echo </span><span style="color: #DD0000">'true' </span><span style="color: #007700">: echo </span><span style="color: #DD0000">'false'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// However, the following examples will work:<br /></span><span style="color: #007700">(</span><span style="color: #0000BB">$some_var</span><span style="color: #007700">) ? print </span><span style="color: #DD0000">'true' </span><span style="color: #007700">: print </span><span style="color: #DD0000">'false'</span><span style="color: #007700">; </span><span style="color: #FF8000">// print is also a construct, but<br /> // it behaves like a function, so<br /> // it may be used in this context.<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$some_var </span><span style="color: #007700">? </span><span style="color: #DD0000">'true'</span><span style="color: #007700">: </span><span style="color: #DD0000">'false'</span><span style="color: #007700">; </span><span style="color: #FF8000">// changing the statement around<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 notes" id="refsect1-function.echo-notes">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">因为是一个语言构造器而不是一个函数，不能被
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<a href="functions.variable_functions.html" class="link">可变函数</a> 调用。
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</span>
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</p></blockquote>
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<div class="tip"><strong class="tip">Tip</strong>
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<p class="para">
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相对 <span class="function"><strong>echo</strong></span> 中拼接字符串而言，传递多个参数比较好，考虑到了 PHP 中连接运算符（“.”）的优先级。
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传入多个参数，不需要圆括号保证优先级：
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</p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">"Sum: "</span><span style="color: #007700">, </span><span style="color: #0000BB">1 </span><span style="color: #007700">+ </span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />echo </span><span style="color: #DD0000">"Hello "</span><span style="color: #007700">, isset(</span><span style="color: #0000BB">$name</span><span style="color: #007700">) ? </span><span style="color: #0000BB">$name </span><span style="color: #007700">: </span><span style="color: #DD0000">"John Doe"</span><span style="color: #007700">, </span><span style="color: #DD0000">"!"</span><span style="color: #007700">;</span>
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</span>
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</pre></div>
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</div>
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<p class="para">
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如果是拼接的，相对于加号和三目元算符，连接运算符（“.”）具有更高优先级。为了正确性，必须使用圆括号：
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</p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">echo </span><span style="color: #DD0000">'Sum: ' </span><span style="color: #007700">. (</span><span style="color: #0000BB">1 </span><span style="color: #007700">+ </span><span style="color: #0000BB">2</span><span style="color: #007700">);<br />echo </span><span style="color: #DD0000">'Hello ' </span><span style="color: #007700">. (isset(</span><span style="color: #0000BB">$name</span><span style="color: #007700">) ? </span><span style="color: #0000BB">$name </span><span style="color: #007700">: </span><span style="color: #DD0000">'John Doe'</span><span style="color: #007700">) . </span><span style="color: #DD0000">'!'</span><span style="color: #007700">;</span>
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</span>
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</pre></div>
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</div>
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</div>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.echo-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="print.html" class="function" rel="rdfs-seeAlso">print</a> - 输出字符串</span></li>
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<li class="member"><span class="function"><a href="printf.html" class="function" rel="rdfs-seeAlso">printf()</a> - 输出格式化字符串</span></li>
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<li class="member"><span class="function"><a href="flush.html" class="function" rel="rdfs-seeAlso">flush()</a> - 刷新输出缓冲</span></li>
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<li class="member"><a href="language.types.string.html#language.types.string.syntax.heredoc" class="link">Heredoc 语法</a></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |