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<HTML
><HEAD
><TITLE
>Syntax and grammar</TITLE
><META
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CONTENT="Modular DocBook HTML Stylesheet Version 1.41"><LINK
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>PHP3 Manual</TH
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><DIV
CLASS="CHAPTER"
><H1
><A
NAME="LANG-SYNTAX"
>Chapter 5. Syntax and grammar</A
></H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="lang-syntax.html#BASIC-SYNTAX"
>Basic Syntax</A
></DT
><DT
><A
HREF="types.html"
>Types</A
></DT
><DT
><A
HREF="variables.html"
>Variables</A
></DT
><DT
><A
HREF="constants.html"
>Constants</A
></DT
><DT
><A
HREF="expressions.html"
>Expressions</A
></DT
><DT
><A
HREF="operators.html"
>Operators</A
></DT
><DT
><A
HREF="control-structures.html"
>Control Structures</A
></DT
></DL
></DIV
><P
>    PHP's syntax is borrowed primarily from C.  Java and Perl have
    also influenced the syntax.

  </P
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="BASIC-SYNTAX"
>Basic Syntax</A
></H1
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="BASIC-SYNTAX.PHPMODE"
>Escaping from HTML</A
></H2
><P
>     There are four ways of escaping from HTML and entering "PHP code
     mode":

    </P
><P
>     <TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="EXAMPLE"
><P
><B
>Example 5-1. Ways of escaping from HTML</B
></P
><PRE
CLASS="PROGRAMLISTING"
>1.  &lt;? echo ("this is the simplest, an SGML processing instruction\n"); ?&#62;
 
2.  &lt;?php echo("if you want to serve XML documents, do like this\n"); ?&#62;

3.  &lt;script language="php"&#62; 
        echo ("some editors (like FrontPage) don't
              like processing instructions");
    &lt;/script&#62;

4.  &lt;% echo ("As of PHP 3.0.4 you may optionally use ASP-style tags"); %&#62;
    &lt;%= $variable; # This is a shortcut for "&lt;%echo .." %&#62;
      </PRE
></DIV
></TD
></TR
></TABLE
>

    </P
><P
>     The first way is only available if short tags have been enabled
     (either by calling <B
CLASS="FUNCTION"
>short_tags()</B
>, they are
     configured on using the short_tags run-time configuration setting,
     or they are enabled using the --enable-short-tags compile-time
     configuration setting.

    </P
><P
>     The fourth way is only available if ASP-style tags have been
     enabled using either the asp_tags configuration setting or the
     --enable-asp-tags compile-time configuration setting.

    </P
><P
>     The closing "bracket" for the block will include the immediately
     trailing newline if one is present.

   </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="BASIC-SYNTAX.INSTRUCTION-SEPARATION"
>Instruction separation</A
></H2
><P
>     Instructions are separated the same as in C or perl - terminate
     each statement with a semicolon.

    </P
><P
>     The closing tag (?&gt;) also implies the end of the statement, so the
     following are equivalent:

     <DIV
CLASS="INFORMALEXAMPLE"
><P
></P
><PRE
CLASS="PROGRAMLISTING"
>&lt;?php
    echo "This is a test";
?&#62;

&lt;?php echo "This is a test" ?&#62;
      </PRE
><P
></P
></DIV
>

   </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="BASIC-SYNTAX.COMMENTS"
>Comments</A
></H2
><P
>     PHP supports 'C', 'C++' and Unix shell-style comments. For example:

    <DIV
CLASS="INFORMALEXAMPLE"
><P
></P
><PRE
CLASS="PROGRAMLISTING"
>&lt;?php
    echo "This is a test"; // This is a one-line c++ style comment
    /* This is a multi line comment
       yet another line of comment */
    echo "This is yet another test";
    echo "One Final Test"; # This is shell-style style comment
?&#62;
     </PRE
><P
></P
></DIV
>

    </P
><P
>     The "one-line" comment styles actually only comment to the
     end of the line or the current block of PHP code, whichever
     comes first.
    </P
><DIV
CLASS="INFORMALEXAMPLE"
><P
></P
><PRE
CLASS="PROGRAMLISTING"
>&lt;h1&#62;This is an &lt;?# echo "simple";?&#62; example.&lt;/h1&#62;
&lt;p&#62;The header above will say 'This is an example'.</PRE
><P
></P
></DIV
><P
>     You should be careful not to nest 'C' style comments, which can
     happen when commenting out large blocks.

    </P
><DIV
CLASS="INFORMALEXAMPLE"
><P
></P
><PRE
CLASS="PROGRAMLISTING"
>&lt;?php
 /* 
    echo "This is a test"; /* This comment will cause a problem */
 */
?&#62;
    </PRE
><P
></P
></DIV
></DIV
></DIV
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>