Why this error is showing? - php

Question

I'm facing a strange error sometimes on my php wap site! Its not persistent, just occurs somwtimes & If I refresh page, error is went out and normal page appears. I'm attaching errors screenshot-
172 line of fun.inc.php is-
return mysql_real_escape_string($str);
I'm pasting line 164 to 212 for better understanding
function clean($str)
{
$str = #trim($str);
if(get_magic_quotes_gpc()) {
$str = stripslashes($str);
$str = str_replace("<",'',$str);
$str = str_replace(">",'',$str);
}
return mysql_real_escape_string($str);
}
function regchars($word){
$chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
for($i=0;$i<strlen($word);$i++){
$ch = substr($word,$i,1);
$nol = substr_count($chars,$ch);
if($nol==0){
return true;
}
}
return false;
}
function nospace($word){
$pos = strpos($word," ");
if($pos === false){
return false;
}else{
return true;
}
}
function checknumber($word){
$chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
$ch = substr($word,0,1);
$sres = ereg("[0-9]",$ch);
$ch = substr($word,0,1);
$nol = substr_count($chars,$ch);
if($nol==0){
return true;
}
return false;
}
function registerform($ef)
{
$errl = "";
switch($ef)
{
Is its a problem of my code or problem from hosting server? How can I prevent users from showing such code??

Answer 1

The function mysql_real_escape_string requires a database connection, so that it can detect what character set is in use and escape correctly.
However, you should not be using that library at all - it is now deprecated. Use either PDO or mysqli, and switch to parameterisation rather than escaping values prior to inserting them yourself.
It seems also that PHP is attempting to connect to the current database as root. Where you do establish a connection, bear in mind that connecting with root is a bad idea. Connect with a user having the least permissions possible for your application to work.

Answer 2

You are not connected to MySQL. You can remove this function if you do not want to do something SQL queries with that.