Can regex fix this?

Question

The page: /index.php?page=6&test=1&test2=2

The code below strip's page=6 off of this so I can add our new page to the url and add the $url_without_page_var back to our link again:

$_SERVER['argv'][0]
// Displays:   page=6&test=1&test2=2

And

 $url_without_page_var=preg_replace('/page=(\d+)/i','',$_SERVER['argv'][0]);
// Displays: &test=1&test2=2

Ok so that code lets me take the page=6 off of page=6&test=1&test2=2 I can then change the page number and add this all back together.

My problem is often the page in the URL will not always be in the same position, it may not be the 1st or last items And this is what will happen when, see how the URL is incorrect now;

/page.php?&test=1&test2=2 ERROR-HERE-ALSO page=9

Is it possible to fix this?

Answer 1

You can just add a new page number at the end of URL without doing anything with old one. Earlier one will be automatically replaced by new one.

If you have a URL

page.php?page=1&var1=foo&var2=bar&page=100

and you check your $_GET array in PHP you will see that $_GET['page'] has value of 100

If you want to replace the value you can use this regex and instead of stripping page number and add it later you could do this in one preg_replace

preg_replace('/(page=)\d+/i', '\1' . $newNumber, $_SERVER['argv'][0]);

That will work no matter which position page is on.

Answer 2

Hi,

you might want to take a look at parse_str, to extract informations from the query string and get them as an array

You then can

• remove the page entry from the array, with unset, for instance
  • or re-define it
• re-construct the query string

For instance :

$str = "first=value&arr[]=foo+bar&arr[]=baz";

parse_str($str, $output);
echo $output['first'];  // value
echo $output['arr'][0]; // foo bar
echo $output['arr'][3]; // baz

And, to get back the remaining pieces togetehr, http_build_query might be useful ;-)

As an example :

$str = 'page=6&test=1&test2=2';
parse_str($str, $data);

var_dump($data);
$data['page'] = 10;

$new_str = http_build_query($data);
var_dump($new_str);

The first var_dump gives you this :

array
  'page' => string '6' (length=1)
  'test' => string '1' (length=1)
  'test2' => string '2' (length=1)

=> You know the page number.

And the second gives you a nice query string :

string 'page=10&test=1&test2=2' (length=22)

Which should be what you need :-)

Answer 3

Modify your regexp to look for an optional trailing ampersand and delete it as well. Then when you put the URL back together, put an ampersand where necessary.

$url_without_page_var=preg_replace('/page=(\d+)\&?/i','',$_SERVER['argv'][0]);
$new_url = $url_without_page_var . '&page=9';

Answer 4

Why can't you just reconstruct the url?

 $query = $_GET;
 unset($query['page']);
 $length = ($length = strpos($_SERVER['REQUEST_URI'], '?')) ? $length : strlen($_SERVER['REQUEST_URI']); 
 $url = substr($_SERVER['REQUEST_URI'], 0, $length) . '?' . http_build_query($query);

http_build_query() does require PHP5 but you could easily rewrite that function.

EDIT: Added the $length variable to fix the code.

Answer 5

The $_GET variable provides an array of all the variables set through the URL. $_REQUEST is an array of all the GET and POST variables set. Here's the fish:

$url_string = "index.php?";
foreach( $_GET as $k => $v ){
    if( $k != "key_you_dont_want"){ // <-- the key you don't want, ie "page"
        if( $url_string != "index.php?" )
            $url_string .= "&"; // Prepend ampersands nicely
        $url_string .= $k . "=" . $v;
    }
}

Regex is a bit overkill for this problem. Hope it makes sense. I've been writing Python and Javascript for the past few weeks. PHP feels like a step backwards.

EDIT: This code makes me happier. I actually tested it instead of blindly typing and crossing fingers.

unset( $_GET["page"] );

$c = count($_GET);
$amp = "";
$url_string = "test.php";

if( $c > 0 ) {
 $url_string .= "?";
 foreach( $_GET as $k => $v ){
  $url_string .= $amp . $k . "=" . $v;
  $amp = "&";
 }
}