Recipe 8.9 Building a GET Query String
8.9.1 Problem
You need to
construct a link that includes name/value pairs in a query string.
8.9.2 Solution
Encode
the names and values with urlencode(
)
and use join( ) to
create the query string:
$vars = array('name' => 'Oscar the Grouch',
'color' => 'green',
'favorite_punctuation' => '#');
$safe_vars = array( );
foreach ($vars as $name => $value) {
$safe_vars[ ] = urlencode($name).'='.urlencode($value);
}
$url = '/muppet/select.php?' . join('&',$safe_vars);
8.9.3 Discussion
The URL built in the solution is:
/muppet/select.php?name=Oscar+the+Grouch&color=green&favorite_punctuation=%23
The query string has spaces encoded as +.
Special characters such as
# are hex-encoded as %23
because the ASCII value of # is 35, which is 23 in
hexadecimal.
Although urlencode( ) prevents any special
characters in the variable names or values from disrupting the
constructed URL, you may have problems if your variable names begin
with the names of HTML entities. Consider this partial URL
for retrieving information about a stereo system:
/stereo.php?speakers=12&cdplayer=52&=10
The HTML entity for ampersand
(&) is & so a
browser may interpret that URL as:
/stereo.php?speakers=12&cdplayer=52&=10
To prevent embedded entities from corrupting your URLs, you have
three choices. The first is to choose variable names that
can't be confused with entities, such as
_amp instead of amp. The second
is to convert characters with HTML entity equivalents to those
entities before printing out the URL. Use htmlentities(
)
:
$url = '/muppet/select.php?' . htmlentities(join('&',$safe_vars));
The resulting URL is:
/muppet/select.php?name=Oscar+the+Grouch&color=green&favorite_punctuation=%23
Your third choice is to change the argument separator from
& to ; by setting the
configuration directive arg_separator.input to
;. You then join name-value pairs with
; to produce a query string:
/muppet/select.php?name=Oscar+the+Grouch;color=green;favorite_punctuation=%23
You may run into trouble with any GET method URLs that you
can't explicitly construct with semicolons, such as
a form with its method set to GET, because your
users' browsers use & as the
argument separator.
Because many browsers don't support using
; as an argument separator, the easiest way to
avoid problems with entities in URLs is to choose variable names that
don't overlap with entity names. If you
don't have complete control over variable names,
however, use htmlentities( ) to protect your URLs
from entity decoding.
8.9.4 See Also
Documentation on urlencode( ) at
http://www.php.net/urlencode and
htmlentities( ) at
http://www.php.net/htmlentities.
|
