[SOLVED] How do I make sure a string is [:alnum:]

[sardonicgem]

Hello folks,

 

I'm trying to check a form field to make sure the user inputs an alphanumeric entry only.

 

The preg_match function does not seem to be the solution.  Any ideas on how to go about this?

[Orio]

Best solution for you would be using ctype_alnum. It's more efficient than using a regular expression, and it does the job.

 

Regex way:

if(preg_match("/[a-z0-9]*/i", $str)) 
{
   //Str is valid
}

 

Orio.

[sardonicgem]

The form field is case sensitive. Also I'm not quite sure how preg_match works.

 

php.net indicates:

 

preg_match() returns the number of times pattern  matches. That will be either 0 times (no match) or 1 time because preg_match() will stop searching after the first match.

 

So suppose my string was "Pa55word"

 

preg_match( '[:alnum:]',"Pa55word")

 

So according to the return value conditions, will preg_match stop searching after P?

[teng84]

that  is why your making a pattern if you make a pattern that will only search for a certain words then your conclusion is applicable here

but if your pattern tries to match not just a word then thats another way

[sardonicgem]

Thanx for the response teng84 but I'm not quite sure I understand what you're talking about.  In my case above will preg_match stop searching after the letter P?  If so,  is there a function that you know of that can search all characters of the input string and confirm that they are all [:alnum:]?

 

 

[Orio]

Yeah yeah my bad. Should be:

 

<?php

if(preg_match("/^[a-z0-9]*$/i", $str)) 
{
   //Str is valid
}

?>

 

 

But I still recommend using the ctype_*() functions.

 

Orio.

[sardonicgem]

Thank you Orio. I ended up using ctype_alnum().