空白變量處理 · smarty3中文手冊

<table summary="Header navigation table" width="100%" border="0" cellpadding="0" cellspacing="0"><tr><th colspan="3" align="center">Smarty - the compiling PHP template engine</th></tr><tr><td width="25%" align="left" valign="bottom"><a href="tips.html" accesskey="P">Prev</a></td><td width="50%" align="center" valign="bottom">Chapter 18. Tips & Tricks</td><td width="25%" align="right" valign="bottom"><a href="tips.default.var.handling.html" accesskey="N">Next</a></td></tr></table> # Blank Variable Handling[空白變量處理] There may be times when you want to print a default value for an empty variable instead of printing nothing, such as printing   so that html table backgrounds work properly. Many would use an {if} statement to handle this, but there is a shorthand way with Smarty, using the default variable modifier. 有時候可能你想打印一個空變量的默認值，而不是空輸出，比如輸出“ ”（這是空格符號的實體，屬于HTML標記）以便表格背景能夠適當地工作。大多數人使用{if}語句來處理這類需要，但這里有一種Smatry的簡寫方法，那就是使用[default](#)變量調節器。 <table width="80%" border="0" cellpadding="2" cellspacing="2" class="note"><caption> 提示 </caption> <tr><td>Note<br/> “Undefined variable” errors will show if PHP xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx and a variable had not been assigned to Smarty.<br/> 如果php xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx（這個是什么跟什么？），同時變量未分配給Smarty，那么會出現“Undefined variable”（變量未定義）錯誤。</td> </tr></table> <table width="100%" border="0" cellpadding="0" cellspacing="0" class="EXAMPLE"><tr><td><div class="EXAMPLE"><a name="AEN4181" id="AEN4181"/> <b>Example 18-1. Printing &nbsp; when a variable is empty</b><br/><b>例 18-1.輸出&nbsp;---如果一個變量是空值</b><table border="0" bgcolor="#E0E0E0" width="100%"><tr><td><pre class="PROGRAMLISTING">{* the long way *}  {if $title eq ""} &nbsp; {else} {$title} {/if}   {* the short way *}  {$title|default:"&nbsp;"}</pre></td></tr></table><p>參見<a href="language.modifier.default.html">default</a>調節器和<a href="tips.default.var.handling.html">默認變量處理</a>。</p></div></td></tr></table> <table summary="Footer navigation table" width="100%" border="0" cellpadding="0" cellspacing="0"><tr><td width="33%" align="left" valign="top"><a href="tips.html" accesskey="P">Prev</a></td><td width="34%" align="center" valign="top"><a href="index.html" accesskey="H">Home</a></td><td width="33%" align="right" valign="top"><a href="tips.default.var.handling.html" accesskey="N">Next</a></td></tr><tr><td width="33%" align="left" valign="top"><p>Tips & Tricks<br/> 使用技巧和經驗</p> </td><td width="34%" align="center" valign="top"><a href="appendixes.html" accesskey="U">Up</a></td><td width="33%" align="right" valign="top"><p>Default Variable Handling<br/> 默認變量處理</p> </td></tr></table>