PHP First Day Supplement

1. Integer overflow: int type number out of range is automatically converted to float type.

2. Variables in single quotes are not compiled.

Variables in double quotes are compiled and automatically replaced with variable content.

3. Output pi with echo pi ();

4. Type conversions for variables.

1. (type) variable name

2.settype (variable name, "type")

5. Determine String type

Is_ type name (variable name)

6. Constant default case sensitive, with define (constant name, "constant")

7. Variable assignment of three ways:

1. Direct assignment $abc= "FGJNLK";

2. Assigning values to variables

$ABC = "Agoijh";

$r = $ABC;

3. Reference Assignment

$ABC = "Agoijh";

$r =& $abc;

The difference between 2 and 3 is that after you change the value of $ABC 2, the value is still not the same, and 3 is changed to the new value.