<HTML ><HEAD ><TITLE >Migrating from PHP 3 to PHP 4</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="PHP Manual" HREF="index.html"><LINK REL="UP" TITLE="FAQ: Frequently Asked Questions" HREF="faq.html"><LINK REL="PREVIOUS" TITLE="Migrating from PHP 2 to PHP 3" HREF="faq.migration.html"><LINK REL="NEXT" TITLE="Miscellaneous Questions" HREF="faq.misc.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=ISO-8859-1"></HEAD ><BODY CLASS="chapter" 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 Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="faq.migration.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="faq.misc.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="chapter" ><H1 ><A NAME="faq.migration4" >Chapter 55. Migrating from PHP 3 to PHP 4</A ></H1 ><P > PHP has already a long history behind him : Legendary PHP 1.0, PHP/FI, PHP 3.0 and PHP 4.0. </P ><DIV CLASS="qandaset" ><DL ><DT >1. <A HREF="faq.migration4.html#faq.migration4.php34" > Migrating from PHP3 to PHP4 </A ></DT ><DT >2. <A HREF="faq.migration4.html#faq.migration4.incompatible" > Incompatible functions? </A ></DT ></DL ><DIV CLASS="qandaentry" ><B ><DIV CLASS="question" ><P ><A NAME="faq.migration4.php34" ></A ><B >1. </B > Migrating from PHP3 to PHP4 </P ></DIV ></B ><DIV CLASS="answer" ><P ><B > </B > PHP 4 was designed to be as compatible with earlier versions of PHP as possible and very little functionality was broken in the process. If you're really unsure about compatibility you should install PHP 4 in a test environment and run your scripts there. </P ><P > Also see the <A HREF="migration4.html" >appropriate migration appendix</A > of this manual. </P ></DIV ></DIV ><DIV CLASS="qandaentry" ><B ><DIV CLASS="question" ><P ><A NAME="faq.migration4.incompatible" ></A ><B >2. </B > Incompatible functions? </P ></DIV ></B ><DIV CLASS="answer" ><P ><B > </B > Since PHP 4 is basically a rewrite of the entire PHP engine there was very few functions that were altered and only then some of the more exotic ones. </P ></DIV ></DIV ></DIV ></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="faq.migration.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="faq.misc.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Migrating from PHP 2 to PHP 3</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="faq.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Miscellaneous Questions</TD ></TR ></TABLE ></DIV ></BODY ></HTML >