10-PHP basic syntax

1. php and HTML mixed encoding.

2. php is case sensitive. $ A = 90 and $ A = 900 are two different values.

3. php declares a variable and assigns a value: $ A = 900;

4. Each line of PHP statement ends with a semicolon.

5. PHP is a weak data type language, which is the same as JavaScript. The data type is determined by context.

6. the PHP variable name must start with a letter or underscore and cannot start with a number. It is the same as Java. Keyword is not recommended.

7. PHP Data Type:

① Basic data type: 1. Integer type 2. Decimal type (single precision, Double Precision) 3. boolean type 4. string type

② Composite data type: 1. array 2. Object

③ Special Data Type: 1. null 2. Resource ($ conn)