php - Check input type value for validation -

i need check input type value must start (wv), , must have 17 additional characters.

for example:

if user write 1223ggg, must show me message:

your entry invalid must wvxxxxxxxxxxxxxxxxx

if user write wv12365478996325874, must show me message:

your entry success

how can that?

casimir's solution might not have worked because want string 19 characters, not 17.

an updated version of be:

if (strpos($str, 'wv')===0 && strlen($str)==19) { 

my regex solution be

if(preg_match('/^wv.{17}$/', 'wv12365478996325874')) {     echo 'your entry success';    } else {     echo 'your entry invalid must wvxxxxxxxxxxxxxxxxx'; } 

if want characters numbers after wv replace . \d.

php demo: https://eval.in/513858
regex101 demo: https://regex101.com/r/mu1kw8/1

depending on need might able use ctype, http://php.net/manual/en/book.ctype.php, validate string.