JScript naming rules

JScript is a case-sensitive language.
The first character must be an ASCII letter (either uppercase or lowercase), or an underscore (_). Note that the first character cannot be a number.
Subsequent characters must be letters, numbers, or underscores.
The variable name must not be a reserved word.
Some examples of the names of legal variables are given below:
_pagecount Part9 Number_items Here are some examples of invalid variable names:
99Balloons//cannot begin with a number. The Smith&wesson//ampersand (&) character is not valid for variable names.

JS and PHP naming rules very much like oh.