Filter Everything Except Letters, Numbers and Dots?

Hello.

I have a dynamic (user input) string called $string.

How do I trunctate every other character except letters (a-zA-Z), numbers (0-9) and dots (allow more than one)?

What I'm trying to do is avoid any kinds of exploits, because I have user inputted URL as a string and I don't want the user entering stuff such as

?><a href="http://wikipedia.com" onClick="window.open('www.google.com');return false;">Free porn</a><?

PHP:

Also, if that's not too much I'm asking: How do I check if it's a valid domain, like
Valid: www.domain.com, domain.com, http://domain.com, http://www.domain.com
Invalid: www.domain.com/post1.html, subdomain.domain.com, www.sub.domain.com, http://domain.com/etc/...

Thanks in advance!

 

For the security problem just use

$string = strip_tags($string);

Code (markup):

 

use these function it validate the domain,subdomain

function urlValidation($url="")
{

if (ereg("^[a-zA-Z0-9\-\.]+\.(aero|asia|biz|cat|com|coop|edu|gov|info|int|jobs|mil|mobi|museum|name|net|org|pro|tel|travel|ac|ad|ae|af|ag|ai|al|am|an|ao|aq|ar|as|at|au|aw|ax|az|ba|bb|bd|be|bf|bg|bh|bi|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gg|gh|gi|gl|gm|gn|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|im|in|io|iq|ir|is|it|je|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|me|mg|mh|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|mv|mw|mx|my|mz|na|nc|ne|nf|ng|ni|nl|no|np|nr|nu|nz|om|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|ps|pt|pw|py|qa|re|ro|rs|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tl|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zr|zw)$",$url))
return true;
else
return false;
}

 

Use preg_replace:

<?php
$string = '<a href="http://wikipedia.com" onClick="window.open(\'www.google.com\');return false;">Free 324234 porn</a>';
$string = preg_replace('/[^0-9a-zA-Z]/'," ",$string);
echo $string;
?>

PHP:

Do you have the domain ready or do you need to parse it out from a paragraph? To simply check a valid domain, use fsockopen if allowed by your host:

$url = 'http://domain.com';

$urlP = parse_url($url);
$host = $urlP["host"];
$fp = @fsockopen($host, 80, $errno, $errstr, 20);
if($fp)
{
     echo 'Domain good';
}

PHP: