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<h1>Cookies</h1>
<p class="para">
PHP transparently supports <acronym title="Hypertext Transfer Protocol">HTTP</acronym> 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 <span class="function"><a href="function.setcookie.html" class="function">setcookie()</a></span> or
<span class="function"><a href="function.setrawcookie.html" class="function">setrawcookie()</a></span>
function. Cookies are part of the <acronym title="Hypertext Transfer Protocol">HTTP</acronym> header, so
<span class="function"><a href="function.setcookie.html" class="function">setcookie()</a></span> must be called before any output is sent to
the browser. This is the same limitation that <span class="function"><a href="function.header.html" class="function">header()</a></span>
has. You can use the <a href="ref.outcontrol.html" class="link">output buffering
functions</a> to delay the script output until you have decided whether
or not to set any cookies or send any headers.
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<p class="para">
Any cookies sent to you from the client will automatically be included into
a <var class="varname"><var class="varname"><a href="reserved.variables.cookies.html" class="classname">$_COOKIE</a></var></var> auto-global
array if <a href="ini.core.html#ini.variables-order" class="link">variables_order</a>
contains "C". If you wish to assign multiple values to a single
cookie, just add <em>[]</em> to the cookie name.
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<p class="para">
Depending on <a href="ini.core.html#ini.register-globals" class="link">register_globals</a>,
regular PHP variables can be created from cookies. However it's not
recommended to rely on them as this feature is often turned off for the
sake of security.
<var class="varname"><var class="varname">$HTTP_COOKIE_VARS</var></var> is also set in earlier versions of PHP
when the <a href="ini.core.html#ini.track-vars" class="link">track_vars</a> configuration
variable is set. (This setting is always on since PHP 4.0.3.)
</p>
<p class="para">
For more details, including notes on browser bugs, see the
<span class="function"><a href="function.setcookie.html" class="function">setcookie()</a></span> and <span class="function"><a href="function.setrawcookie.html" class="function">setrawcookie()</a></span>
function.
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