Regular Experssion for Email Address - PHP

**sstaubin01** · Dec 5, 2000 13:53

I'm trying to build a Regular Expression used with PHP to edit a form field containing an Email Address. I need the field to include a @ and a . otherwise it is an invaild value. The Regular Expressions I have experimented with use an 'or' operator but this must be an 'and' operator. The text must include a @ and . The Regular Expression [@.] is true if the text includes @ or .

Any suggestions?

**Son Nguyen** · Dec 5, 2000 14:31

Here is the pattern I have, spot out any error if you see!

Code:

^[_\.0-9a-z-]+@([0-9a-z][0-9a-z-]+\.)+[a-z]{2,3}$

**sstaubin01** · Dec 5, 2000 14:43

Thanks 123. I don't know what all that means. My examples were much simplier. I'll research the logic, try it out and let you know if I find any problems. Thanks again.

**firepages** · Dec 5, 2000 19:26

This is the one I use - it aint perfect but it allows
me.at@this.com.au etc which some routines do not

<?
function vmail($email) {global $res;
$re="^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$";
if(eregi($re,$email)){$res="pass";} else { $res="fail";}
}?>

It will however allow bad ones like this@that.com.me.you.doh

**Son Nguyen** · Dec 5, 2000 19:53

Yeah, this is good!
I though .+ would accept any character, but when I tested your function with +=..., it failed (which is excellent!)

So do we have an optimal solution for this problem?

**sstaubin01** · Dec 5, 2000 21:41

Can you guys tell me what's wrong with this. It accepts anything.

// Regular Expression for validating emailaddr.
function vmail($emailaddr) {global $emailspecialcharerror;
$re="^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$";
if(eregi($re,$emailaddr)){$emailspecialcharerror = 'yes'; $error = 'yes';}}

123 says it works. I must be doing something wrong.

**freddydoesphp** · Dec 5, 2000 21:59

This one seems to work well for me:

function bad_email($emailtotest) {
return eregi("(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)", $emailtotest, $arr_vars) OR !eregi ("^.+\@(\[?)[-a-zA-Z0-9\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$", $emailtotest, $arr_vars);
}

if (bad_email("john@johnson.com")) {
print "Email Bad";
}
else {
print "Email good";
}

**Son Nguyen** · Dec 5, 2000 22:23

Originally posted by sstaubin01
Can you guys tell me what's wrong with this. It accepts anything.

// Regular Expression for validating emailaddr.
function vmail($emailaddr) {global $emailspecialcharerror;
$re="^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$";
if(eregi($re,$emailaddr)){$emailspecialcharerror = 'yes'; $error = 'yes';}}

123 says it works. I must be doing something wrong.

For the else part, you should set it to be something else.

**sstaubin01** · Dec 5, 2000 23:30

I tried Freddy's pattern and it works as coded in the post although it has the same problem as Firepages stated. It accepts aa@aa.aa.bb.ccc. A great deal of respect goes out the the people who figure this stuff out. Thanks all for the help.

**freddydoesphp** · Dec 6, 2000 00:40

but that is valid haven't you seen email address like

someone@univ.tenn.edu

or someone@streets.ca.gov

**Son Nguyen** · Dec 6, 2000 00:55

Freddy, do you mind to explain the pattern you had?

Code:

(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)

Could you list a case for each "or" you had?

Thanks, since I just want to learn more about reg. exp.

**firepages** · Dec 6, 2000 03:54

if(eregi($re,$emailaddr)){$emailspecialcharerror = 'yes'; $error = 'yes';}}

should be
if(eregi($re,$emailaddr)){//this is good//}else{//this is bad//}

and yes its good to allow '.com.au' for instance but it still does not cover silly stuff like .com.au.haha.yuk etc

and I have never figured out a bit of REGEX in my life ! (well almost never) - this is an old javascript one I 'borrowed' from I know not where, but it gets used every day so far with no probs, apart from the odd joker trying to see if he/she can pass dodgy code.

**freddydoesphp** · Dec 6, 2000 11:48

Son,

eregi("(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)|(\.$)

This says that if there are
(@.*@) = two @ in email address
(\.\.) = two .. right next to each other in the address
(@\.) = two @. right next to each other in the address
(\.@) = two .@ right next to each other in the address
(^\.) = one . right at the beginning of the address
//This one was missing from the above(\.$) = one . right at the end of the address

**jumpthru** · Dec 6, 2000 21:20

Just take a brief over look of this thread, from top to bottom.

Now you know why most programmers go crazy (and probably why so many newbies get scared off).

**Son Nguyen** · Dec 8, 2000 21:41

Originally posted by freddydoesphp
Son,

eregi("(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)|(\.$)

This says that if there are
(@.*@) = two @ in email address
(\.\.) = two .. right next to each other in the address
(@\.) = two @. right next to each other in the address
(\.@) = two .@ right next to each other in the address
(^\.) = one . right at the beginning of the address
//This one was missing from the above(\.$) = one . right at the end of the address

Nice! Do you think we could catch all the cases?
And one interesting thing: for the new domains (.info, .aero,...) the ending match will fail (only allows 2,3 chars)

**freddydoesphp** · Dec 8, 2000 22:09

Should be easy enough to fix
function bad_email($emailtotest) {
return eregi("(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)", $emailtotest, $arr_vars) OR !eregi ("^.+\@(\[?)[-a-zA-Z0-9\.]+\.([a-zA-Z]{2-4}|[0-9]{2-4})(\]?)$", $emailtotest, $arr_vars);
}

What else would you like to see it catch?

**Son Nguyen** · Dec 8, 2000 22:17

Well,

Code:

([a-zA-Z]{2-4}|[0-9]{2-4})(\]?)$

Should it be {2,4} instead of "-"?

Yeah, I think it's more than enough when it could catch those invalid email! Or else your visitor will yell and let you know why their email got rejected!!

**freddydoesphp** · Dec 8, 2000 22:46

You are correct Sir!

That is what I get for posting before I test

**Son Nguyen** · Dec 9, 2000 09:43

Originally posted by freddydoesphp
You are correct Sir!

That is what I get for posting before I test

LOL!
About the fix for new domains (4chars), it is easy but I believe MANY error checking patterns are in use will fail. Let see the effect in Jan 2001 (is that the time we are allowed to use those domain??)

**FatPiper** · Feb 21, 2001 02:46

Ok,
I know this isn't regex, but anyways... Would this correctly check a file for a certain email address and return true if it was there and false if not (or vice versa...):

Code:

function email_already_exists($emailtotest) {
return eregi($emailtotest,implode(file($listfile),""),$arr_vars);
}

Thanks!

**Kevin Yank** · Feb 21, 2001 10:51

The dots in the email address have a special meaning when used as a regular expression. Better to use a simpler (and faster) string search function:

Code:

function email_already_exists($emailtotest) {
  return (substr_count(implode(file($listfile),""),$emailtotest) > 0);
}

**FatPiper** · Feb 21, 2001 16:23

I see ...
And so I could use that as in

Code:

if (!email_already_exists($emailaddress)){
do blahblah; }

and it'll do it only if the email address is not already in the file? or would I need something like

Code:

if (!email_already_exists($emailaddress)>0){
do blahblah;}

Thanks a lot for your help
BTW: the script this is being used for is here:
http://www.dannycook.com/index.php3?...le=mailinglist
this actually includes it but you can see the basic functionality. source code is at
http://www.dannycook.com/source/mailinglist.php3.txt
(edit)The rest of the php source code for the site is in that directory as well:
http://www.dannycook.com/source/(end edit)

Thanks!

**Kevin Yank** · Feb 21, 2001 19:57

Your first code fragment is correct. The function converts the numeric result to true/false already.

**FatPiper** · Feb 22, 2001 03:50

Ok, great ... Nothing like SP!

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