How to write a basic check for an invalid email address

Question

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How to validate an email address in PHP

Below I have a piece of code where it checks for a valid email address:

if ( (strlen($getemail) >= 7) && (strstr($getemail, "@")) && (strstr($getemail, ".")) ){

But what my question is that what is the opposite of the code above so that I can check if the email typed in does not contain all of the features above?

In any case, `!allOfFeatures` is the "opposite" of `allOfFeatures`; the boolean-logic negation can be applied through `&&` (and `||`) operators by De Morgan's, here are two answers I wrote on it in general: http://stackoverflow.com/questions/12169639/why-ssi-condition-doesnt-work?lq=1, http://stackoverflow.com/questions/6115801/how-do-i-test-if-a-variable-does-not-equal-either-of-two-values/6115869#6115869 (and they have sufficient detail for the "logic" of such inversions) — , Dec 10 '12 at 01:03

score 3 · Answer 1 · answered Dec 10 '12 at 00:57

PHP already has a function that can do this for you. It's called filter_var and what you're looking for is the validation filter for FILTER_VALIDATE_EMAIL.

Example:

if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    // It's a valid email address
} else {
    // It's not a valid email address
}

score 2 · Answer 2 · answered Dec 10 '12 at 01:27

It seems to me that what are you trying to do can be achieved be RegEx.

var_dump(preg_match('#^(\w+){7,}@(\w+)\.([a-z]){2,4}$#i', 'example@example.com')); # 1 (true)
var_dump(preg_match('#^(\w+){7,}@(\w+)\.([a-z]){2,4}$#i', 'foo@example.com')); # 0 (false)

If one of the conditions is not met (make sure address is alphanumeric, 7 chars minimum, followed by @, etc.), entire expression would result in false value.

Example:

if(preg_match('#^(\w+){7,}@(\w+)\.([a-z]){2,4}$#i', $email))
{
// do stuff
}

Do not validate email like that, use inbuilt filter_var function. There is no real way of validating if email is "real", main problem are domains, TLDs that is.

score 0 · Accepted Answer · edited Dec 10 '12 at 01:12

0

if (!( (strlen($getemail) >= 7) && (strstr($getemail, "@")) && (strstr($getemail, ".")) )){

edited Dec 10 '12 at 01:12

Mxyk

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answered Dec 10 '12 at 00:53

James McDonnell

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How to write a basic check for an invalid email address

3 Answers3