<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >empty("0")</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="PHP 手册" HREF="index.html"><LINK REL="UP" TITLE="从 PHP 3 移植到 PHP 4" HREF="migration4.html"><LINK REL="PREVIOUS" TITLE="初始化" HREF="migration4.initializers.html"><LINK REL="NEXT" TITLE="缺少的函数" HREF="migration4.missing.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=UTF-8"></HEAD ><BODY CLASS="section" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >PHP 手册</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="migration4.initializers.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >附录 D. 从 PHP 3 移植到 PHP 4</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="migration4.missing.html" ACCESSKEY="N" >下一页</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="section" ><H1 CLASS="section" ><A NAME="migration4.empty" ><TT CLASS="literal" >empty("0")</TT ></A ></H1 ><P > 可能最具争议的改变是对 <A HREF="function.empty.html" ><B CLASS="function" >empty()</B ></A > 函数行为的改变。一个仅包含字符“0”(是零,不是英文字母“O”)的字符串现在被认为是空字符串,而 PHP 3 中则相反。 </P ><P > 这个改变对 web 程序很有意义,所有的 input 表单返回的都是 string,甚至填写的是数字。PHP 能够自动进行类型转换。但另一方面,这可能不是代码的原意,可能导致代码莫名其妙的错误。 </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="migration4.initializers.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >起始页</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="migration4.missing.html" ACCESSKEY="N" >下一页</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >初始化</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="migration4.html" ACCESSKEY="U" >上一级</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >缺少的函数</TD ></TR ></TABLE ></DIV ></BODY ></HTML >