Begining PHP notes

Week of 1/12/2003

Variables- things that can change depending on circumstances.

1. The reference to a variable begins with a $ (The variable from the form if in html, does not have the $ )
2. They are case sensitive
3. The can't start with a number following the $
4. Try to avoid Pre-existintg or Built in Functions
5. Variables can be declared simply by setting a value.Types of variables: Defined by first instance of the assigned value- Also can be reassigned uppon reassignment in subsequent instances.
   1. Integer- whole numbers Ex. $totalquantity=0
   2. Double- Real numbers EX. $totalamount=0.00
   3. String- Characters
   4. Array- Multiple data or table
   5. Object- an object.
6. Scope of the variable can be Global (the entire script), Local (just for this instance) or local to global.

Constants- Things that do not change within the course of the scripts

1. The are represented in all upper case letters
2. There is no $ in front of a constant.
3. Can be defined by the simple assignment as follows:

   define ("TIREPRICE", 100);
    

Operators- are used to signify mathmatical operations.

1. Operator examples
   1. =  is an assignment
   2. + add
   3. - subtrack
   4. / divide
   5. * multiply
   6. . concatonate (append)
2. Applies to numbers
3. Strings will have a value of 0 when used in these expresssions.