urlencode — URL-encodes
string urlencode ( string $str )
This function is convenient when encoding a string to be used in a query part of a URL, as a convenient way to pass variables to the next page.
str - The string to be encoded.
Returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. It is encoded the same way that the posted data from a WWW form is encoded, that is the same way as in application/x-www-form-urlencoded media type. This differs from the » RFC 3986 encoding (see rawurlencode()) in that for historical reasons, spaces are encoded as plus (+) signs.
<?php echo '<a href="mycgi?foo=', urlencode($userinput), '">'; ?>
<?php $query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar); echo '<a href="mycgi?' . htmlentities($query_string) . '">'; ?>