Notice: Undefined variable: bla bla

[rocoso]

Hi phpfreaks!!

 

Ive been wondering...  Sometimes i get "Notice: Undefined variable: .... "    I usually do a error_reporting(0);  or define it like $blabla = "";  somewhere in the beginning of my script.  How bad is a Undefinded variable ?  The script still works.  I just dont want no errors at all.

 

 

 

 

 

 

 

 

[Barand]

At best, it's bad programming practice to reference variables that haven't been initialised.

 

At worst, your script won't work. See trivial example below. I recommend you use error_reporting(E_ALL) when developing you scripts.

 

Example

<?php
include 'db.php';

error_reporting(E_ALL);

if (isset($_POST['username']))
{
$username = $_POST['username'];
$password = $_POST['password'];
$sql = "SELECT password FROM users WHERE username = '$username'";
$res = mysql_query($sql);
if ($row = mysql_fetch_row($res))
{
	if ($pasword == $row[0])                            // undefined variable - never logs in
	{
		exit("Login successful");
	}
}
}
?>
<form method='post'>
       Username <input type="text" name="username" size="12"> <br>
       Password <input type="text" name="password" size="12"> <br>
       <input type="submit" name="btnSubmit" value="Log in">
</form>

[Daniel0]

At worst, your script won't work. See trivial example below. I recommend you use error_reporting(E_ALL) when developing you scripts.

 

And turn them off when the script is running on a live site. Expose as little information as possible to potential attackers.

[PFMaBiSmAd]

The display_errors setting should be used on a live server to prevent the display of errors, but error_reporting should be left as E_ALL. This still allows error logging to show unexpected conditions, such as un-caught conditions with data verification that you might need to address in your code (maybe a search script keeps failing because commonly entered values are causing notices/warnings) or things like a hacker submitting deliberately invalid data to your script to see if he can break in. When warnings or notices are disabled, you don't have any record of what went wrong.