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<chapter id="features">
<title>PHP3 features</title>
<simpara></simpara>
<sect1 id="feature-httpauth">
<title>HTTP authentication with PHP</title>
<simpara>
The HTTP Authentication hooks in PHP are only available when it is
running as an Apache module. In an Apache module PHP script, it
is possible to use the <function>Header</function> function to
send an "Authentication Required" message to the client browser
causing it to pop up a Username/Password input window. Once the
user has filled in a username and a password, the URL containing
the PHP script will be called again with the variables,
$PHP_AUTH_USER, $PHP_AUTH_PW and $PHP_AUTH_TYPE set to the user
name, password and authentication type respectively. Only "Basic"
authentication is supported at this point.
<para>
An example script fragment which would force client authentication
on a page would be the following:
<example>
<title>HTTP Authentication example</title>
<programlisting role=php>
<?php
if(!isset($PHP_AUTH_USER)) {
Header("WWW-Authenticate: Basic realm=\"My Realm\"");
Header("HTTP/1.0 401 Unauthorized");
echo "Text to send if user hits Cancel button\n";
exit;
} else {
echo "Hello $PHP_AUTH_USER.<P>";
echo "You entered $PHP_AUTH_PW as your password.<P>";
}
?>
</programlisting></example>
<para>
Instead of simply printing out the $PHP_AUTH_USER and
$PHP_AUTH_PW, you would probably want to check the username and
password for validity. Perhaps by sending a query to a database,
or by looking up the user in a dbm file.
<para>
Watch out for buggy Internet Explorer browsers out there. They
seem very picky about the order of the headers. Sending the
<emphasis>WWW-Authenticate</emphasis> header before the
<errorcode>HTTP/1.0 401</errorcode> header seems to do the trick
for now.
<para>
In order to prevent someone from writing a script which reveals
the password for a page that was authenticated through a
traditional external mechanism, the PHP_AUTH variables will not be
set if external authentication is enabled for that particular
page.
<para>
Note, however, that the above does not prevent someone who
controls a non-authenticated URL from stealing passwords from
authenticated URLs on the same server.
<sect1 id="feature-images">
<title>GIF creation with PHP</title>
<simpara>
PHP is not limited to creating just HTML output. It can also be
used to create GIF image files, or even more convenient GIF image streams.
You will need to compile PHP with the GD library of image functions for
this to work.
</simpara>
<para>
<example>
<title>GIF creation with PHP</title>
<programlisting role=php>
<?php
Header("Content-type: image/gif");
$string=implode($argv," ");
$im = imagecreatefromgif("images/button1.gif");
$orange = ImageColorAllocate($im, 220, 210, 60);
px = (imagesx($im)-7.5*strlen($string))/2;
ImageString($im,3,$px,9,$string,$orange);
ImageGif($im);
ImageDestroy($im);
?>
</programlisting></example>
This example would be called from a page with a tag like:
<img src="button.php?text">
The above button.php3 script then takes this "text"
string an overlays it on top of a base image which in this case
is "images/button1.gif" and outputs the resulting
image. This is a very convenient way to avoid having to draw
new button images every time you want to change the text of a
button. With this method they are dynamically generated.
</para>
<sect1 id="feature-fileupload">
<title>File upload support</title>
<simpara>
PHP is capable of receiving file uploads from any RFC-1867 compliant
browser. This feature lets people upload both text and binary
files. With PHP's authetication and logical functions, you have full
control over who is allowed to upload and what is to be done with the
file once it has been uploaded.
</simpara>
<para>
A file upload screen can be built by creating a special form which looks
something like this:
<example>
<title>File Upload Form</title>
<programlisting>
<FORM ENCTYPE="multipart/form-data" ACTION="_URL_" METHOD=POST>
<INPUT TYPE="hidden" name="MAX_FILE_SIZE" value="1000">
Send this file: <INPUT NAME="userfile" TYPE="file">
<INPUT TYPE="submit" VALUE="Send File">
</FORM>
</programlisting></example>
The _URL_ should point to a php html file. The MAX_FILE_SIZE hidden
field must precede the file input field and its value is the maximum filesize
accepted. The value is in bytes. In this destination file, the following
variables will be defined upon a successful upload:
<para>
<itemizedlist>
<listitem><simpara>$userfile - The temporary filename in which the uploaded file was stored on
the server machine.</simpara></listitem>
<listitem><simpara>$userfile_name - The original name of the file on the sender's system.</simpara></listitem>
<listitem><simpara>$userfile_size - The size of the uploaded file in bytes.<simpara></listitem>
<listitem><simpara>$userfile_type - The mime type of the file if the browser provided this information.
An example would be "image/gif".</simpara></listitem>
</itemizedlist>
Note that the "$userfile" part of the above variables is whatever the name of
the INPUT field of TYPE=file is in the upload form. In the above upload form example,
we chose to call it "userfile".
<simpara>
Files will by default be stored in the server's default temporary directory. This
can be changed by setting the environment variable TMPDIR in the environment in which
PHP runs. Setting it using a PutEnv() call from within a PHP script will not
work though.
<simpara>
The PHP script which receives the uploaded file should implement whatever
logic is necessary for determining what should be done with the uploaded file.
You can for example use the $file_size variable to throw away any files that are
either too small or too big. You could use the $file_type variable to throw away
any files that didn't match a certain type criteria. Whatever the logic, you should
either delete the file from the temporary directory or move it elsewhere.
<simpara>
Please note that the CERN httpd seems to strip off everything starting at
the first whitespace in the content-type mime header it gets from the
client. As long as this is the case, CERN httpd will not support the
file upload feature.
<sect1 id="feature-cookies">
<title>HTTP cookie support</title>
<para>
PHP transparently supports HTTP cookies. Cookies are a mechanism for storing data in
the remote browser and thus tracking or identifying return users.
You can set cookies using the <function>setcookie</function> function. Cookies are
part of the HTTP header, so the SetCookie() function must be called before any output
is sent to the browser. This is the same restriction as for the <function>Header</function>
function.
<para>
Any cookies sent to you from the client will automatically be turned into a PHP
variable just like GET and POST method data. If you wish to assign multiple values to
a single cookie, just add <emphasis>[]</emphasis> to the cookie name.
For more details see the <function>setcookie</function> function.
</para>
<sect1 id="feature-databases">
<title>Database support</title>
<simpara>
PHP supports a number of different databases in both native mode and through ODBC.
</simpara>
<sect1 id="feature-regexps">
<title>Regular expressions</title>
<para>
Regular expressions are used for complex string manipulation in PHP. The functions
that support regular expressions are:
<itemizedlist>
<listitem><simpara><function>ereg</function></listitem>
<listitem><simpara><function>ereg_replace</function></listitem>
<listitem><simpara><function>eregi</function></listitem>
<listitem><simpara><function>eregi_replace</function></listitem>
<listitem><simpara><function>split</function></listitem>
</itemizedlist>
These functions all take a regular expression string as their first argument. PHP uses
the Posix extended regular expressions as defined by Posix 1003.2. For a full description
of Posix regular expressions see the regex man pages included in the regex directory in
the PHP distribution.
</para>
<para>
<example>
<title>Regular expression examples</title>
<programlisting>
ereg("abc",$string); /* Returns true if "abc" is found anywhere in $string. */
ereg("^abc",$string); /* Returns true if "abc" is found at the beginning of $string. */
ereg("abc$",$string); /* Returns true if "abc" is found at the end of $string. */
eregi("(ozilla.[23]|MSIE.3)",$HTTP_USER_AGENT); /* Returns true if client browser is Netscape 2, 3 or MSIE 3. */
ereg("([[:alnum:]]+) ([[:alnum:]]+) ([[:alnum:]]+)",$string,$regs); /* Places three space separated words into $regs[1], $regs[2] and $regs[3]. */
ereg_replace("^","<BR>",$string); /* Put a <BR> tag at the beginning of $string. */
ereg_replace("$","<BR>",$string); /* Put a <BR> tag at the end of $string. */
ereg_replace("\n","",$string); /* Get rid of any carriage return characters in $string. */
</programlisting></example>
</para>
<sect1 id="feature-error-handling">
<title>Error handling</title>
<simpara>
All <link linkend="lang-expr">PHP expressions</link> can be called
with the "@" prefix, which turns off error reporting for that
expression. If an error occured during such an expression and the
<link linkend="ini.track-errors">track_errors</link> feature
is enabled, you can find the error message in the global variable
$php_errormsg.
</simpara>
<sect1 id="feature-source-viewer">
<title>PHP source viewer</title>
<simpara></simpara>
</chapter>
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