Regex for 2 letters followed by 4 digits

Question

The string should begin with \"S2\" followed by any 4 digits.

A matching string is \"S20165\".

I\'m trying with the following code, but it always echos OK ev

Answer 1

You need to match the start and end of the string too

/^S2[0-9]{4}$/

Answer 2

$string='S20104';
if(preg_match('/^S2[0-9]{4}$/', $string)){
    echo 'OK';
}
else{
    echo 'NOT OK';
}

Answer 3

you missed the start^ and end$

'/^S2[0-9]{4}$/'

Answer 4

You have to use anchors:

/^S2[0-9]{4}$/

^ matches the start of the string and $ matches the end of the string, so this will make sure that you check the complete string and not just a substring.

You can also use \d instead of [0-9]. In PHP, as long as you do not use the 'u' pattern modifier, preg* functions are not Unicode aware, so the two are equivalent.

Answer 5

The problem is that preg_match searches for a match anywhere inside the string.

S2123456
^^^^^^
matches

You can anchor your regular expression using ^ (start of line) and $ (end of line):

'/^S2[0-9]{4}$/'

• See it working online: ideone
• Read more about anchors: regularexpresssions.info/anchors.html