Regular expression help

graham

Hi,

I've written a basic search engine for a site and need to ensure that user's don't use wildcards.

So, I thought that regular expressions may be the way to go to strip any non-alpha characters out of their input string before passing it through the search engine expression building code. I only want users to be able to input a-z, A-Z or a space, but I don't know how to create the correct preg_replace(). Can anyone please educate me? I can then use this, together with a book, to learn why it works and not be so dumb in the future (well, hopefuly)

So, to clarify, I have

$input_string = "d*ff%g jfk12dkld&"

and I want to use a preg_replace to get

"dffg jfkdkld" as the result

13th_seer

that's a pretty simple regex

all you have to do is filter all characters NOT in the set of A through Z, a through z, and space

the regex for that is /[^A-Za-z ]/

everything in the brackets is a set of single characters. the ^ means NOT one of the following characters .. and the hyphen just means to use an ASCII range from the char before to the char after the hyphen

some example code (depending on your ver of php you may have to change the PHP_SELF and GET vars ..)

<html>

<head>
</head>

<body>

<form action='<?=$GLOBALS['PHP_SELF']?>' method='get'>

<input name='query' type='text' value='<?=htmlentities($_GET['query'],ENT_QUOTES)?>'>
<input type='submit' value='search'>

</form>

<?php

if (@$_GET['query'])
{
	$query = preg_replace("/[^A-Za-z ]/","",$_GET['query']);
}

?>

original query was - <b><?=$_GET['query']?></b>
<br>
filtered query is - <b><?=$query?></b>

</body>
</html>

simpler regular expressions aren't that hard. the rules are all simple, it's just putting lots of them together that makes them so ugly and intimidating

do a google search for 'regular expression tutorial' to learn more