Variable names must start with a ‘$’ character (to allow the php parser to work as fast as possible by instantly know it is a variable).
A variable name must start with a letter of the alphabet or and underscore ‘_’.
Variable names may only contain: ‘a’ – ‘z’, ‘A’ – ‘Z’ and ‘_’
Variable names are case sensitive.
PHP will always convert a variable to the type requried by the contect it is being used in.
$number = 12345 & 67890; //$number is used as a numeric varaible echo substr ($number, 3, 1); //$number is used as a string
Use in functions to retain a value between calls.
static $LastPostTitle = "";
Note that whilst you can assign an initial value, it must not be the result of an expression (e.g. “= 2 + 4” is not allowed)
Every line of code in your program can access a global variable.
Note that you can’t use = when declaring a global variable. Assign the value seperately.
Integer size is platform-dependent, safest is to assume a maximum value of about two billion (32 bits signed).
64-bit platforms usually have a maximum value of about 9E18
Unsigned integers are not supported in PHP
If PHP encounters a number, or the result of an operation, that is beyond the bounds of the integer type, it will be interpreted as a float instead.