PHP表单。 需要检查第一个字母[关闭]

Question

In a form I have an ID field, which needs to check that the first letter is "P" and is 5 characters long.

I have looked into preg_match but I have no idea how to get it working. It seems to be able to check how many "P"s the would be and where they are, but how do I get that to check that only entries starting with "P" are passed.

Big time PHP noobie so doesn't need to be anything awesome. I really don't get PHP. :(

Answer 1

To check if a string starts with P and is 5 characters long, using preg_match, as you asked for, I would write (lazily)

<?php
  if (preg_match('/^P....$/', $your_ID_variable) === 1) {
    print 'your ID is starting with a P and is 5 characters long.';
  }
?>

But as posted from others, there are other ways to do it, like:

<?php
   if ((strlen($your_ID_variable) == 5)
   && (strpos($your_ID_variable, 'P') === 0)) {
    print 'your ID is starting with a P and is 5 characters long.';
   }
?>

Here are some sources you could have found:

• http://www.php.net/manual/en/regexp.reference.meta.php
• http://www.php.net/manual/en/function.preg-match.php
• http://www.php.net/manual/en/function.strlen.php
• http://www.php.net/manual/en/function.strpos.php