Regular expression needed for specific string in PHP - regex

Question

I need a regular expression to validate a string with the following conditions
String might contain any of digits space + - () / .
If string contain anything else then it should be invalid
If there is any + in the string then it should be at the beginning and there should at most one + , otherwise it would be invalid, if there are more than one + then it is invalid
String should be 7 to 20 character long
It is not compulsory to have all these digits space + - () / .
But it is compulsory to contain at least 7 digit

Answer 1

I think you are validating phone numbers with E.164 format. Phone number can contain many other format. It can contain . too. Multiple spaces in a number is not uncommon. So its better to format all the numbers to a common format and store that format in db. If that common format is wrong you can throw error.
I validate those phone numbers like this.
function validate_phone($phone){
// replace anything non-digit and add + at beginning
$e164 = "+". preg_replace('/\D+/', '', $phone);
// check validity by length;
return (strlen($e164)>6 && strlen($e164)<21);
}
Here I store $e164 in Db if its valid.
Even after that you can not validate a phone number. A valid phone number format does not mean its a valid number. For this an sms or call is generated against the number and activation code is sent. Once the user inputs the code phone number is fully validated.

Answer 2

You can do this in one regex:
/^(?=(?:.*\d){7})[0-9 ()\/+-][0-9 ()\/-]{6,19}$/
However I would personally do something like:
/^[0-9 ()\/+-][0-9 ()\/-]{6,19}$/
And then strip any non-digit and see if the remaining string is 7 or longer.

Answer 3

Let's try ...
preg_match('/^(?=(?:.*\d){7})[+\d\s()\/\-\.][\d\s()\/\-\.]{6,19}$/', $text);
Breaking this down:
We start with a positive look-ahead that requires a digit at least 7 times.
Then we match all the valid characters, including the plus.
Followed by matching all the valid characters without plus between 6 and 20 times.

Answer 4

A little more concise:
^\+?(?=(.*\d){7})[()/\d-]{7,19}$
'Course, why would you even use regular expressions?
function is_valid($string) {
$digits = 0;
$length = strlen($string);
if($length < 7 || $length > 20) {
return false;
}
for($i = 0; $i < $length; $i++) {
if(ctype_digit($string[$i])) {
$digits++;
} elseif(strpos('+-() ', $string[$i]) === false && ($string[$i] !== '+' || $i !== 0)) {
return false;
}
}
return $digits >= 7;
}