[Resolved] regex ereg/eregi

bfuzze_98

I'm trying to block strings containing punctuation and characters other than a-z, 0-9, _, and . (period). Regex. I've been looking through the other pages and have found a number of possible solutions, but none of them seem to work. I don't really understand the syntax of these functions (esp. preg_match, etc.) which makes it very difficult to debug.

First I tried:

if(eregi("[a-z0-9_.]*", $fname)) 
{}
else {
//error message
}

result: everything passes.

I tried some other examples using ereg, eregi, or pregmatch, strstr, and strpos. In all cases, the result was either everything passes or nothing passes. It's not catching the errors. What am I doing wrong?

wilku

I'll use preg_match, because the manual says it's faster:

<?php
$fname[] = "abr234akadabra?txt";
$fname[] = "abr234akadabra/txt/";
$fname[] = "abr234akadabra\\txt";
$fname[] = "\"abr234akadabratxt";
$fname[] = "abr234akad.YYYabra_txt";
foreach ($fname as $str)
if(preg_match('|^[a-z0-9_.]*$|i', $str))
{
   echo "<i>$str</i> <b>passed</b> the test.<br>";
}
else {
     echo "<i>$str</i> <b>failed</b>.<br>";
}
?>

And now some explanation. In regular expression "|" means the beginning and the end of regex. After the end there is an option "i", meaning the search should be case insensitive. The main difference however lies in "^" and "$". They mean that the match should start at the beginning and end with the end of a string. Without it, preg_match looks for any substring. So in the first string it finds "abr234akadabra" even though the next character, question mark, isn't valid. The result without ^$ would be true. With them, it's false.

Oh, and the result of the script above is:

abr234akadabra?txt failed.
abr234akadabra/txt/ failed.
abr234akadabra\txt failed.
"abr234akadabratxt failed.
abr234akad.YYYabra_txt passed the test.

bodzan

...when learning the basics of regular expressions...

http://www.regular-expressions.info/

bfuzze_98

Wilku,

Thnk you for the detailed explanation, I appreciate it. I will give this a try this evening.

Bodzan,

Thanks for the reference.

bfuzze_98

This worked well, thanks again.