php else block not getting called

Question

I am noob in php and I have spent many hours trying to understand why my else block is not getting called. I have tried number of things but just not sure why it is not getting called. I am sure its something stupid i am doing.

     <?php   
 $base_url = 'http://localhost/mine/';
     $per_page = 3;                           //number of results to shown per page 
     $num_links = 8;   
     $cur_page = 1;                          // set default current page to 1

if(isset($_REQUEST['string'])<>'') 
{
      $search_string = " title LIKE '%".mysql_real_escape_string($_REQUEST["string"])."%' OR description LIKE '%".mysql_real_escape_string($_REQUEST["string"])."%'";
      $query = mysql_query("SELECT * FROM products WHERE ".$search_string);
      $row = mysql_num_rows($query) or die(mysql_error());

      $row = $row; 

      $cur_page = $_GET['page'];
      $cur_page = ($cur_page < 1)? 1 : $cur_page; 
      $offset = ($cur_page-1)*$per_page;                //setting offset

      $pages = ceil($row/$per_page);              // no of page to be created


      $start = (($cur_page - $num_links) > 0) ? ($cur_page - ($num_links - 1)) : 1;
      $end   = (($cur_page + $num_links) < $pages) ? ($cur_page + $num_links) : $pages;

      $res  =   mysql_query("SELECT * FROM products WHERE ".$search_string." ORDER BY title LIMIT ".$per_page." OFFSET ".$offset);  

      while($row=mysql_fetch_array($res))
         {
         include ('form.php');
         }
    }
      else
     include ('alert.php');

    ?>

i forgot to add that i am using the get method for the url's . So i think it might be possible that even when there is no search term it is still showing index.php?string= which would mean that it is still taking the if statement as true and not going to the else statement. Please correct me if i am wrong.

here is a snippet from my pagination.php

if (strstr($_SERVER['REQUEST_URI'], "?string="))
        {
            echo '<span id="prev"> <a href="' . $_SERVER['PHP_SELF'] . '?string=' . $_GET['string'] . '&page=' . (1) . '">' . $dir . '</a> </span>';
        }
        else
            echo '<span id="prev"> <a href="' . $_SERVER['PHP_SELF'] . '?page=' . (1) . '">' . $dir . '</a> </span>';

Try to add curly braces and if it doesn't works well add `echo` for debugging step by step. — ChoiZ, Dec 16 '13 at 21:00
`<>` is SQL syntax. The PHP equivalent would be `!=` therefore your `if(isset($_REQUEST['string'])<>'')` should be `if(isset($_REQUEST['string'])!='')` — Funk Forty Niner, Dec 16 '13 at 21:02
curly braces is not necessary when is just one statement after the if/else @user602525, ChoiZ — Emilio Gort, Dec 16 '13 at 21:02
<> works perfectly fine in PHP. <> and != are actually 100% interchangeable. That comment is invalid. — skrilled, Dec 16 '13 at 21:11
What version of PHP are you using? I am unable to reproduce your error with PHP 5.5.3. — Mike, Dec 16 '13 at 21:18
The problem is that "isset(xyz) <> ''" is *ALWAYS TRUE*. POSSIBLE SOLUTION: `if (!isset(xyz) && xyz <> '')`. BETTER SOLUTION: `if (!empty(xyz))`. — paulsm4, Dec 16 '13 at 21:30
@user3077454 - my comment is correct. The problem is your "if()". The best solution - which I noticed Chosen Wann posted 1/2 hour ago - is to substitute "!empty()". Please upvote and select Chosen Wann's response. — paulsm4, Dec 16 '13 at 21:35

score 2 · Answer 1 · answered Dec 16 '13 at 21:02

Your IF-condition is wrong

isset returns true or false it does not return a value that could be compare to empty or what is between your quotes

if(!empty($_REQUEST['string']))

The above if statement should be enough to check if the value is set and if it's not empty\

Some things you should read

isset() vs empty() vs is_null()

empty()'s documentation

Funk Forty Niner · Answer 2 · 2013-12-16T21:20:35.193

2

OP's condition could also be written as if(!isset($_REQUEST['string']))

EDIT : I was wrong earlier about:

<> is SQL syntax

The PHP equivalent would be != therefore your if(isset($_REQUEST['string'])<>'') should be if(isset($_REQUEST['string'])!='')

edited Dec 16 '13 at 21:20

answered Dec 16 '13 at 21:03

Funk Forty Niner

74,450
15
68
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$a <> $b Not equal TRUE if $a is not equal to $b after type juggling. is valid http://www.php.net/manual/en/language.operators.comparison.php for more info – Emilio Gort Dec 16 '13 at 21:07
`<>` you can perfectly use that operator, it's not only SQL Syntax. PHP uses it too. – Ali Dec 16 '13 at 21:09
Yes, I just noticed that now. @ChosenWann – Funk Forty Niner Dec 16 '13 at 21:10
Which could also be written as `if(!isset($_REQUEST['string']))` – Funk Forty Niner Dec 16 '13 at 21:11
@Fred-ii- Exactly, but I think the OP also wanted to check whether it was empty or not, so using `empty` only is sufficient for what the user needs. – Ali Dec 16 '13 at 21:12
It's hard to actually pinpoint what the OP is looking to get out of `string`, since we don't see the form or where `string` is being called from. @ChosenWann – Funk Forty Niner Dec 16 '13 at 21:14
Just saw it now. The OP added extra code to the question. @ChosenWann – Funk Forty Niner Dec 16 '13 at 21:15
After seeing OP's added code, the `!empty` on your part makes more sense. @ChosenWann – Funk Forty Niner Dec 16 '13 at 21:18

score 0 · Answer 3 · answered Dec 16 '13 at 20:59

Use

if(isset($_REQUEST['string'])) { /*...*/ } else { /*...*/ }

or

if($_REQUEST['string'] != '') { /*...*/ } else { /*....*/ } (while the latter probably throwing a warning in case of the parameter string was not passed at all)

Not both at the same time like you did.

score 0 · Answer 4 · answered Dec 16 '13 at 21:00

0

Try using this as the condition for the IF:

if(isset($_REQUEST['string']) && trim($_REQUEST['string'])!=''){ ...

First it will check if the variable exists, and if it does, it will check if it has some text in it - just in case

answered Dec 16 '13 at 21:00

Catalin

773
1
7
18

score 0 · Answer 5 · answered Dec 16 '13 at 21:26

To understand why it's not working, we need to break it apart into parts.

First, you are comparing the value of isset($_REQUEST['string']) (which will always return a boolean) to an empty string.

If you do

var_dump(isset($_REQUEST['string']));

You should see either bool(true) or bool(false) as the output depending on if it's set.

However when you compare a boolean to a string, it will be type cast the boolean into a string so that both types are the same.

var_dump( (string) false ); // Outputs string(0) ""
var_dump( (string) true ); // Outputs string(1) "1"

So you are essentially doing the following:

// When $_REQUEST['string'] is unset
if ("" <> "") { ... } // Will always be false because "" === ""

// When $_REQUEST['string'] is set
if ("1" <> "") { ... } // Will always be *true* because "1" != ""

So therefore, the reason must be that $_REQUEST['string'] is, in fact, unset. I have tested this myself in PHP 5.5.3:

$set_var = 'i_am_set';
var_dump( isset($set_var) <> '' ); // Outputs bool(true)
var_dump(  isset($unset_var) <> '' ); // Outputs bool(false)

However, I think that what you're looking for is empty() which will return false if the variable is either unset or empty.

score 0 · Answer 6 · edited May 23 '17 at 12:03

0

Could be in this way, your say you'w using GET method

$string = isset($_GET['string']) ? $_GET['string'] : NULL;

if(!empty($string ){
   //your stuff
}

Side Note: read this link How can I prevent SQL injection in PHP?

edited May 23 '17 at 12:03

Community

1
1

answered Dec 16 '13 at 21:26

Emilio Gort

3,475
3
29
44

1

You're mixing up `[]`s and `()`s and also didn't put a `$` in front of `string`. – Mike Dec 16 '13 at 22:04

jsgrosman · Answer 7 · 2013-12-16T21:18:43.710

-2

isset() has a boolean return value.

See http://www.php.net/isset.

You should just be able to use it in the if clause.

if(isset($_REQUEST['string'])) 
{

}
else
{

}

You can also use array_key_exists(). See http://www.php.net/function.array-key-exists. This doesn't actually check to make sure that the request parameter has a useful value.

if(array_key_exists('string', $_REQUEST)) 
{

}
else
{

}

empty() will check for an array key, null, and no value. That's what I'd use.

if(!empty($_REQUEST['string'])) 
{

}
else
{

}

edited Dec 16 '13 at 21:18

answered Dec 16 '13 at 21:03

jsgrosman

1
1

1

This only fulfills the user's first condition which is checking if `$_REQUEST['string']` is set or not, it does not fulfill his second condition. – Ali Dec 16 '13 at 21:07
I assume you mean, if the request parameter has any value. You're probably right empty() is what's called for here. – jsgrosman Dec 16 '13 at 21:16

php else block not getting called

7 Answers7