preg_match does not work - php

Question

This script checks if there is a special character or not, if there is, it calls for the preg match's "Invalid" function, else it says username available. What happens here is that every time I write a special character like ##%^& it still says username available instead of saying invalid, and that's not how it's supposed to work. I have checked the PHP code for errors and it seemed to be clean. I have tried and run to everything on forums and couldn't find a solution. Your contribution will be so much appreciated!
if(isset($_POST['login'])) {
$login = mysql_real_escape_string($_POST['login']);
if(!empty($login)) {
$login_query = mysql_query("SELECT COUNT(`id`) FROM `account` WHERE `login` = '$login'");
$login_result = mysql_result($login_query,0);
if($login_result == 0) {
echo 'yes';
} else {
echo 'no';
}
}
}
if ( preg_match("/^[a-zA-Z0-9[:space:]]+$/" , $login) ) {
echo 'noinput';
}
P.S I am not some kid who has leeched a code from the internet and is trying to get the others to do the work for him, I have written like 70% of this script and it works pretty well except the special characters thingy which I'm so stuck with. I hope you can help me. Thank you!

Answer 1

Not sure what your problem is. I just wrote the following program:
<?php
$input="good string";
$input2="bad#string";
if (preg_match("/^[a-zA-Z0-9[:space:]]+$/",$input2)) {
echo $input2." matches\n";
}
else {
echo $input2." does not match\n";
}
if (preg_match("/^[a-zA-Z0-9[:space:]]+$/",$input)) {
echo $input." matches\n";
}
else {
echo $input." does not match\n";
}
And it correctly shows that $input matches, but $input2 does not.
Are you sure of what is in your input? Could there be a carriage return?
update I think it is simply a case of you misinterpreting the return values of the php script. Let's look at the options:
1) valid username, is available:
query is empty, print string "yes". The preg_match finds a match and prints "noinput".
2) valid username, not available:
query returns something, print string "no". preg_match prints "noinput"
3) invalid username, is available:
query is empty, print string "yes". The preg_match prints nothing.
4) invalid username, not available:
query returns something, prints string "no". preg_match prints nothing.
If that is not how you interpret the return values, that's your problem...
second update
I have just looked at the source code of your link, and this is indeed the problem. You seem to test for several different responses:
if(data=='no') {
// do stuff
} else {
// something else
});
}
if(data=='noinput') {
// more stuff
});
}
if(data=='invalid') {
// yet more stuff
});
In other words, you check for strings 'yes', 'no', 'noinput'. But the way your code is structured and run, this is not the output you produce. For which I refer you to the four cases above.
solution
You need to move the check for invalid inputs to earlier in the code; and you need to return immediately after finding a user name that does not match. I think the following will work:
if(isset($_POST['login'])) {
$login = mysql_real_escape_string($_POST['login']);
if ( preg_match("/^[a-zA-Z0-9[:space:]]+$/" , $login) )
{
$login_query = mysql_query("SELECT COUNT(`id`) FROM `account` WHERE `login` = '$login'");
$login_result = mysql_result($login_query,0);
if($login_result == 0)
{
echo 'yes';
}
else
{
echo 'no';
}
}
else
{
echo('noinput');
}
}

Answer 2

It doesn't appear your regular expression accounts for special characters. You'll need to add in the characters you want to catch outside of numbers and alpha.
Look here for some advice: http://www.regular-expressions.info/characters.html
Try something like /^[a-zA-Z0-9\$[:space:]]+$/
The \$ accounts for the literal character.