check user input is numeric or character string data

[yllai]

i have a form (in php) for user to submit their information...for example: postcode, i need to makesure user entering numeric value for postcode but not character string after user clcik on 'Submit'..how can i do it? same as otherwise, i need to makesure user not entering numeric value for field that require character string value.

Any example?

[ergophobe]

Let's say the field is called postcode, I do

if (  isset($_POST['postcode'])  
  && is_numeric($_POST['postcode'])  
  && is_int($_POST['postcode'] + 0) 
  ) 

basically, line by line
- is the variable set?
- post data from an <input> is a string, so we check whether the string is numeric
- if it is, we cast it as a number (which type depends on the data) by adding zero (or multiplying by 1) and check to see whether the number is an integer of a float.

Tom