PHP：url参数

i have a question about formatting the URL parameters in php

page 1 can have these 2 url

http://somewhere.com/page1.php?foo=1
and
http://somewhere.com/page1.php

now on page 1, when i click a button, i want it to redirect to its self but with an additional parameters in the URL like so

http://somewhere.com/page1.php?foo=1&bar=2
or
http://somewhere.com/page1.php?bar=2

depending on the current url. How can i do this in php?

thanks, Vidhu

First, check if a certain $_GET parameter is set, using isset.
If it is, echo a certain link. If not, echo a different link.

if( !isset($_GET['bar']) ){
    echo '<a href="?bar=2">link</a>';
}
else{
    echo '<a href="page1.php">link</a>';
}

The following form will submit to the same url with parameters added.

<form action="<?php echo "http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI']; ?>" method="get">
    <?php
        // Iterate through our query string and add each key value pair as a hidden input
        foreach ($_GET as $key => $value)
        {
            ?>
                <input type="hidden" name="<?php echo $key; ?>" value="<?php echo $value; ?>"/>
            <?php
        }
    ?>

    <!-- new parameter to add -->
    <input type="hidden" name="foo" value="1"/>
    <input type="submit"/>
</form>

You can do a simple get system, So you will need to check if ?foo=1 is set if it is you can echo its content. If you want to show content for bar=2 check if its set and echo its content. This is just a simple way there more ways though.

Simply you can do with $_SERVER['PHP_SELF']

For example

<form action="<?php echo htmlentities($_SERVER['PHP_SELF']); ?>" method="get">
    <input type="hidden" name="foo" value="1"/>
    <input type="submit"/>
</form>

Here the htmlentities() is used to avoid PHP_SELF exploitation as a security precaution

If you wish to avoid hidden input fields you can append the query parameters like action="<?php echo $_SERVER['PHP_SELF']; ?>?foo=1&bar=2"

I'm using these PHP functions to help me build urls correctly:

• parse_str()
• parse_url()
• http_build_query()
• http-build-url()

Example:

<?php

function add_parameters($parameters) {
    parse_str($_SERVER['QUERY_STRING'], $old_parameters_as_array);
    return $_SERVER['PHP_SELF'].'?'.http_build_query(array_merge($old_parameters_as_array, $parameters));
}

echo '<a href="'.add_parameters(array('bar' => 2)).'">Link</a>';