PHP regex: each word must end with dot

Question

Can someone help me how to specific pattern for preg_match function?

• Every word in string must end with dot
• First character of string must be [a-zA-Z]
• After each dot there can be a space
• There can't be two spaces next to each other
• Last character must be a dot (logicaly after word)

Examples:

• "Ing" -> false
• "Ing." -> true
• ".Ing." -> false
• "Xx Yy." -> false
• "XX. YY." -> true
• "XX.YY." -> true

Can you help me please how to test the string? My pattern is

/^(([a-zA-Z]+)(?! ) \.)+\.$/

I know it's wrong, but i can't figure out it. Thanks

Answer 1

Check how this fits your needs.

/^(?:[A-Z]+\. ?)+$/i

• ^ matches start
• (?: opens a non-capture group for repetition
• [A-Z]+ with i flag matches one or more alphas (lower & upper)
• \. ? matches a literal dot followed by an optional space
• )+ all this once or more until $ end

Here's a demo at regex101

If you want to disallow space at the end, add negative lookbehind: /^(?:[A-Z]+\. ?)+$(?<! )/i

Answer 2

Try this:

$string = "Ing
Ing.
.Ing.
Xx Yy.
XX. YY.
XX.YY.";

if (preg_match('/^([A-Za-z]{1,}\.[ ]{0,})*/m', $string)) {
    // Successful match
} else {
    // Match attempt failed
}

Result:

The Regex in detail:

^               Assert position at the beginning of a line (at beginning of the string or after a line break character)
(               Match the regular expression below and capture its match into backreference number 1
   [A-Za-z]        Match a single character present in the list below
                      A character in the range between “A” and “Z”
                      A character in the range between “a” and “z”
      {1,}            Between one and unlimited times, as many times as possible, giving back as needed (greedy)
   \.              Match the character “.” literally
   [ ]             Match the character “ ”
      {0,}            Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
)*              Between zero and unlimited times, as many times as possible, giving back as needed (greedy)