php-doc-en/language/basic-syntax.xml

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  <chapter id="language.basic-syntax">
   <title>Basic syntax</title>

   <!--
   
    NOTE:                             Last modified: 2001-05-16 13:00 GMT
    
    the language part is currently under heavy revision. Please do not
    not make any heavy (i.e. structural) modifications to this part 
    for a moment. 
    
    You'd also better not start any translation yet.
    
    Comments are always welcome at phpdoc@lists.php.net
    
    Progress:
    
     intro : DOESN'T EXIST - yet?
             new chapter, with some introductionary remarks?
             Will be discussed on the ML soon.
     basic-syntax: 
             FINISHED
             except maybe moving the 'advanced escaping'
             to a better place?
             TODO: 
              - nada
     types : Being revised. Added all new types
             Boolean and Integer are more or less finished.
             The rest isn't.
             TODO: 
              - why is $foo[bar] bad syntax?
              - what's the difference between unset($bla) and
                $bla = NULL; (it is different!)
              - $obj->{expr} syntax
              - (unset) cast?????
              - $bla = unset <== should've been nuked, don't mention it
              - $str{offset} syntax, rather than $str[offset]
              - read notes and apply when any of them are useful
              - remove notes which have been included here.
              - ...
     the rest: Not yet started with.
             TODO: 
              - ?
     oop   : has been revised by Kristian, DONE.
   -->
   
   <sect1 id="language.basic-syntax.phpmode">
    <title>Escaping from HTML</title>
  
    <para>
     When PHP starts to handle file, it will just output the text
     it encounters. So if you have a HTML-file, and you change its
     extension to .php, your file will keep working.
    </para>

    <para>
     If you want to insert php-statements at some point in your
     file, you'll need to indicate so to php, by entering "PHP mode"
     in either of the following ways:
    </para>

    <para>
     <example>
      <title>Ways of escaping from HTML</title>
      <programlisting>
1.  &lt;? echo ("this is the simplest, an SGML processing instruction\n"); ?&gt;
    &lt;?= expression ?&gt;  This is a shortcut for "&lt;? echo expression ?&gt;"
    
2.  &lt;?php echo("if you want to serve XHTML or XML documents, do like this\n"); ?&gt;

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

4.  &lt;% echo ("You may optionally use ASP-style tags"); %&gt;
    &lt;%= $variable; # This is a shortcut for "&lt;%echo .." %&gt;
      </programlisting>
     </example>
    </para>

    <para>
     The first way is only available if short tags have been
     enabled. This can be done 
     <!-- via the <function>short_tags</function> function,-->
     by enabling the <link linkend="ini.short-open-tag">short_open_tag</link>
     configuration setting in the PHP config file, or by compiling PHP with the
     --enable-short-tags option to <command>configure</command>.
    </para>

    <para>
     The second way is the generally preferred method, as it allows for the
     next generation of XHTML to be easily implemented with PHP.
    </para>

    <para>
     The fourth way is only available if ASP-style tags have been
     enabled using the <link linkend="ini.asp-tags">asp_tags</link>
     configuration setting.

    <note>
     <para>Support for ASP-style tags was added in 3.0.4.</para>
    </note></para>

    <para>
     The closing tag for the block will include the immediately
     trailing newline if one is present.
    </para>
    
    <para> <!-- TODO: find a better place for this para -->
     PHP allows you to use structures like this:
     <example><title>Advanced escaping</title>
     <programlisting role="php">
&lt;?php

if (boolean-expression) {
    ?&gt;
&lt;strong&gt;This is true.&lt;/strong&gt;
    &lt;?php
} else {
    ?&gt;
&lt;strong&gt;This is false.&lt;/strong&gt;
    &lt;?php
}
    ?&gt;
     </programlisting></example>
     
     This works as expected, because PHP handles text within ?&gt; and
     &lt;?php as an <function>echo</function> statement.
     <!-- without the parsing if vars, that is (hopefully?) obvious -->
    </para>

   </sect1>

   <sect1 id="language.basic-syntax.instruction-separation">
    <title>Instruction separation</title>

    <simpara>
     Instructions are separated the same as in C or perl - terminate
     each statement with a semicolon.</simpara>

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

     <informalexample>
      <programlisting>
&lt;?php
    echo "This is a test";
?>

&lt;?php echo "This is a test" ?>
      </programlisting>
     </informalexample></para></sect1>

   <sect1 id="language.basic-syntax.comments">
    <title>Comments</title>
   
    <para>
     PHP supports 'C', 'C++' and Unix shell-style comments. For example:

    <informalexample><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
?>
     </programlisting>
    </informalexample></para>

    <simpara>
     The "one-line" comment styles actually only comment to the
     end of the line or the current block of PHP code, whichever
     comes first.</simpara>
     <informalexample><programlisting>
&lt;h1>This is an &lt;?php # echo "simple";?> example.&lt;/h1>
&lt;p>The header above will say 'This is an example'.
     </programlisting></informalexample> 

    <simpara>
     You should be careful not to nest 'C' style comments, which can
     happen when commenting out large blocks.</simpara>

    <informalexample><programlisting>
&lt;?php
 /* 
    echo "This is a test"; /* This comment will cause a problem */
 */
?>
    </programlisting></informalexample></sect1>
  </chapter>
 
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