Regex in PHP that allows alphanumeric with one space only

Question

How can I build a regex that allows alphanumeric and only one space like :

MM56M pass
MM 54M pass
MMM 5
555555 pass
LPOLKG pass
MM 5T YU does not pass

Thanks

See [Learning Regular Expressions](http://stackoverflow.com/a/2759417/3832970). — Wiktor Stribiżew, Jan 20 '16 at 21:32
why not simply count the spaces and check, if more then 1? (without regex) — Jarlik Stepsto, Jan 20 '16 at 21:33
Possible duplicate of [Learning Regular Expressions](http://stackoverflow.com/questions/4736/learning-regular-expressions)... https://regex101.com/r/hQ6fM4/2.. — chris85, Jan 20 '16 at 21:42
duplicate: http://stackoverflow.com/questions/4287602/php-preg-match-needed-to-ensure-only-one-space-character-is-allowed-between-word — RomanPerekhrest, Jan 20 '16 at 21:46
Sorry it is not a duplicate topic the answer given is not working for ZZZ Z ZZ as string , there is 2 spaces and the regex ^[a-zA-Z]+( [a-zA-Z]+)*$ does not check that. you can test here: https://regex101.com/ — oussama kamal, Jan 20 '16 at 21:55
`echo (trim($str, "a..zA..Z0..9") === " ") ? ☺ : "(⊙＿⊙)"; ` — Andrew, Jan 20 '16 at 21:55
If `ZZZ Z ZZ` is a valid string your question doesn't cover that.. — chris85, Jan 21 '16 at 02:49

RedLaser · Answer 1 · 2016-01-20T21:41:53.217

1

Would this work:

^[A-Za-z0-9]+( [A-Za-z0-9]+)?$

It matches one or more any-case letters or numbers then possibly a space and one or more any-case letters or numbers

edited Jan 20 '16 at 21:41

answered Jan 20 '16 at 21:39

RedLaser

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You would also want to anchor the the start/end of the string or else this will just match any substring and pass validation. Also, OP doesn't say, but is the space required. – Jonathan Kuhn Jan 20 '16 at 21:41
my bad, hopefully fixed it @oussamakamal – RedLaser Jan 20 '16 at 21:42

score 0 · Answer 2 · answered Jan 20 '16 at 22:14

This regex should work...

/^[[:alnum:]]+( [[:alnum:]]+)?$/

Demo: https://regex101.com/r/hQ6fM4/2 (not the g modifier being used here won't be used in PHP, if the string is multi-lined use the m so the ^$ affect each line).

The [[:alnum:]] is a posix character bracket for an alpha or numerical character. The + after is a quantifier meaning one or more of those characters. The ^$ are anchors the ^ is the start of the string, the $ is the ending. The () is a grouping and the ? after makes that whole second group optional. The / are delimiters telling where the regex starts and ends.

or if you want a strange approach:

$str = 'test test';
$post = preg_replace('/\s/', '', $str);
if (((strlen($str) - 1) == strlen($post) || (strlen($str) == strlen($post))) && ctype_alnum($post)) {
echo  'tis good';
} else {
 echo 'rut row';
}

Demo: https://eval.in/505494

Regex in PHP that allows alphanumeric with one space only

2 Answers2