preg_match multiple expressions

Question

hi guys i was wondering how could i build e regExp that says:

"this string may contain 1-25 letters that are not these specific words:"root","bin","download","shutdown"

So I thought:

$dang_words="/(root)|(bin)|(shutdown)|(download)/";
$reg_exp="/^[a-z]{1,25}$/";

if(preg_match($reg_exp,$field) || !preg_match($dang_words,$field))
{
 echo "your input it's okkk!";
}
else 
 echo "this is a bad word!!";

But it's not working

why?

thanks

Luca

Do you mean that the string must not be one of the bad words or must not contain one of the bad words? So, would rubinia be allowed or not? — Tim Pietzcker
– Tim Pietzcker, Commented Feb 24, 2011 at 18:05
i just want to allow alphabet letters but dont wont any dangerous word! — luca
– luca, Commented Feb 24, 2011 at 18:52

amitchd · Accepted Answer · 2011-02-24 18:06:06Z

5

$dangerous_words="/(root)|(bin)|(shutdown)|(download)/";
$reg_exp="/^[a-z]{1,25}$/";

if(preg_match($reg_exp,strtolower(trim($field))) && !preg_match($dangerous_words,strtolower(trim($field))))
{
 echo "your input it's okkk!";
}
else 
 echo "this is a bad word!!";

You have your logical operators messed up.. Just changed from || to &&.

answered Feb 24, 2011 at 18:06

amitchd

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Comments

ircmaxell · Accepted Answer · 2011-02-24 19:31:40Z

4

Close... Try this:

/^(?!.*(root|bin|shutdown|download))[a-z]{1,25}$/

It uses a forward assertion

So, it becomes:

if (preg_match('/^(?!.*(root|bin|shutdown|download))[a-z]{1,25}$/', $content)) {
    echo "Your input is ok";
} else {
    echo "there is a bad word/invalid content";
}

edited Feb 24, 2011 at 19:31

answered Feb 24, 2011 at 18:04

ircmaxell

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3 Comments

ircmaxell Over a year ago

Care to explain the -1? It works in one regex instead of two...?

brett rogers Over a year ago

I guess it depends on the interpretation of his intent. Your single regex is different than the combination of his 2 regexes. Yours only flags the string as bad if the string is an exact match for one of the bad words. His method flags the string as bad if the string contains one of the bad words anywhere in the string.

ircmaxell Over a year ago

@brett: thanks, I didn't realize that. But knowing that now, I can fix that problem ;-)

lockdown · Accepted Answer · 2011-02-24 18:03:05Z

0

I think your issue lies with all the ( ). In some old code I created a while ago I used this:

$stopInjectionVerbs = "/(alter|begin|cast|convert|create|cursor|declare|delete|drop|end|exec|fetch|insert|kill|open|select|sys|table|update)/";
$errors = array();

if (preg_match($stopInjectionVerbs, $select)) {
    $errors[] = "Can not use SQL injection Strings";
}

This all works correctly. Have a go without the brackets around each individual word.

answered Feb 24, 2011 at 18:03

lockdown

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1 Comment

luca Over a year ago

I just tested against('root') without all those brackets.. and it still says "your input it's ok!!!"

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