7 replies to this topic

[thatsme]

Hi, this line if (empty($_POST['userName'])) worked well on wamp 2.1, but strange things started to happen when i uploaded my code to host. Now this line sometimes returns true and sometimes false no matter that i always pass unempty string from form. Even at times when empty returns true, line echo $_POST['userName'] prints the value I typed in which means that $_POST['userName'] should have returned false . Any help?

[Vaielab]

Can you post some code

[thatsme]

The code is here:

<?php
    require_once("stdlib.php");
    require_once("sqlInjectionPreventer.php");
    $con = connectToDatabase();
    
    mysql_select_db("wlv_warfarehistory", $con);
    
    if (empty($_POST['userName']))
        printErrorMessage("Username is not filled in");
    $username = htmlentities($username);
    $username = SqlInjectionPreventer::cleanQuery($username);...

I can post further code if needed

[Vaielab]

First you should always test if the variable exist like so:

if (isset($_POST['userName'])) ...

Second, if you wish to test if their anything enter in this variable you should use

strlen(trim($_POST['userName']))

insted of empty.
From php.net manual:
Returns FALSE if var has a non-empty and non-zero value.
The following things are considered to be empty:
"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)

So empty do more than just looking for a empty string

[Alexander]

A silly trick, however isset($_POST['foo'][0]) can check for both existence, an non-emptiness in one call.

[Vaielab]

Alexander said:

A silly trick, however isset($_POST['foo'][0]) can check for both existence, an non-emptiness in one call.

I did not know about the fact that isset can test multiple level at the same time
I was certain that I needed to test if($_POST['foo']) and after if($_POST['foo'][0])
Is this a new thing or it always been like that?
I actually create my own method to test this with a huge while to test every level of the array

[Alexander]

Quote

I did not know about the fact that isset can test multiple level at the same time

In C, strings are simply arrays of individual characters - and PHP extends this trait in to itself.

$name = "Alexander";
echo $name[0] . $name[strlen($name) - 1];

Would print "Ar".

And

$array = array('abc', '123');
echo $array[0][0];

Would print 'a'.

This could be of course used in the example to ensure there is at least one character (0th index of string.)

[thatsme]

Thanks. Now i use isset and strlen(trim($_POST($field))) == 0 to check if the value was filled in in the field. it works fine