String regex checks

netfrugal

I'm trying to understand something concerning regular expressions. I haven't had too much luck understanding the basics I guess. But I'm working at a simple alphanumeric check on a variable.

For example, a person's name should not have a number. So, if the javascript fails, or isn't turned on for a browser, I'd like some checks from the server side.

$name= "John Smith 4";

if(preg_match("[0-9]",$name)){ echo "invalid name"; }else{ echo "valid name";  }

I must be missing something to this statement. Because I'm always getting the "valid name" response returned back.

laserlight

For PCRE, you need to use pattern delimiters. For example:

$name= "John Smith 4";

if(preg_match("/[0-9]/",$name)){ echo "invalid name"; }else{ echo "valid name";  }

Of course, in this case you could just write:

$name= "John Smith 4";

if(preg_match('/\d/',$name)){ echo "invalid name"; }else{ echo "valid name";  }

I suggest using single quote delimited strings for your regex patterns.

Also, you should check for valid names instead of invalid names. Otherwise, you may miss out on an invalid combination.