regex not working!

[sid0972]

following is the regex to match several words,letters and spaces, but it seems i got it wrong.

 

$expr='/^[a-zA-Z0-9 ]*{2,36}$/';

if(preg_match($expr,$input))
 {
   echo "good ";
 }
 else
 {
   echo "not good";
 }

 

can anyone tell me Whats wrong?

[sid0972]

nevermind i found it.

 

function check_system($input)
{
$expr = '/^[0-9a-zA-Z ]+$/';

if(preg_match($expr,$input))
 {
   return true;
 }
 else
 {
   return false;
 }
}

[Christian F.]

To those who're wondering: The problem was that you had used two quantifiers. Both * (zero, or many) and {2,36} (between 2 and 36, inclusive).

[sid0972]

oh ok

is there any way i can tell if there's a problem with a regex, or i just have to look at it?

[Christian F.]

If the RegExp doesn't work as intended, then there's a problem with it. Especially if it spits out an error message. There are also tools that validate regular expressions, but you have to be careful with what dialect they validate for.

Other than that, there's no other way than to look at it and (trying to) understand what it does.