Null is not the value it is the lack of value.
isset() function determines whether a variable is set or not.
Empty values are : “”, null, 0, 0.0, “0”, false, array().
Its not a best practice to depend on type juggling.
Settype() and Gettype() are used for type casting by default.
Settype() conversion is done in placed.
Constants value can't change if we reassign a value to the constant even it is impossible to redefine the constants again.
If statement check that whether the condition is true or not.
If condition is true then execute the statement.
Learn multiple case for one statement.
foreachloop is more effective in the case of associative array.