Basic PHP knowledge (2)

Automatic data type conversion: 1. After the integer type is added or subtracted, it is still an integer type. If the integer type can be divisible, the result is an integer type; otherwise, the result is a real type; 2. During addition, subtraction, multiplication, division, and division of integer and real types, the integer type is converted to the real type, and the calculation result is still the real type. 3. When a string is involved in the operation, it is truncated from the string to the first character to the phase

Automatic data type conversion: 1. After the integer type is added or subtracted, it is still an integer type. If the integer type can be divisible, the result is an integer type; otherwise, the result is a real type; 2. During addition, subtraction, multiplication, division, and division of integer and real types, the integer type is converted to the real type, and the calculation result is still the real type. 3. When a string is involved in the operation, it is truncated from the string to the first character to the phase

Automatic data type conversion:

1. After the integer type is added or subtracted, it is still an integer type. If the integer type can be divisible, the result is an integer type; otherwise, the result is a real type;

2. During addition, subtraction, multiplication, division, and division of integer and real types, the integer type is converted to real type, and the calculation result is still real type;

3. When a string is involved in the operation, it is truncated from the string to the first character and converted to the corresponding value (either an integer or a real character );

4. When the boolean type is converted to a number, true indicates 1 false indicates 0;

Forced conversion of data types:

1. When the real type is forcibly converted to an integer, the decimal point is unsigned unconditionally (int) $

2. the integer type is forcibly converted to the real type (float) $

3. Forcibly convert an integer to a string (string) $

4. boolean type forced conversion to INTEGER (int) $ a true indicates 1 false indicates 0

5. boolean type forced conversion to string (string) $ a true indicates '1' false indicates''

6. Forcibly convert numeric type to boolean type (boolean) $ a if it is not 0, true 0 is false.

7. Forcibly convert a string to a boolean (boolean) $ a if it is not null, true if it is null, false

The following content of the operator is excerpted from (Http://www.w3school.com.cn/php/php_operators.asp)

Reference Value assignment: $ a = & $ B points the memory address of $ B to $ a. Changing $ B is equivalent to changing $.

Arithmetic Operator:

Operator	Name	Example	Result
+	Addition	$ X + $ y	Sum of $ x and $ y
-	Subtraction	$ X-$ y	Difference between $ x and $ y
*	Multiplication	$ X * $ y	The product of $ x and $ y
/	Division	$ X/$ y	$ X and $ y
%	Module	$ X % $ y	$ X remainder except $ y

Assignment operator:

Assignment	Equivalent	Description
X = y	X = y	The expression on the right sets the value for the number of operations on the left.
X + = y	X = x + y	Add
X-= y	X = x-y	Subtraction
X * = y	X = x * y	Multiplication
X/= y	X = x/y	Division
X % = y	X = x % y	Module

String OPERATOR:

Operator	Name	Example	Result
.	Concatenation	$ Txt1 = "Hello" $ txt2 = $ txt1. "world! "	Now $ txt2 contains "Hello world! "
. =	Serial assignment	$ Txt1 = "Hello" $ txt1. = "world! "	Now $ txt1 contains "Hello world! "

Increment/decrease OPERATOR:

Operator	Name	Description
++ $ X	Ascending	$ X increment by one, and then returns $ x
$ X ++	Post-Increment	Returns $ x, and increments by $ x plus one.
-- $ X	Decrease before	$ X minus one decrease, and then returns $ x
$ X --	Decrease	Returns $ x, and then decreases by $ x.

Comparison operator:

Operator	Name	Example	Result
=	Equal	$ X = $ y	Returns true if $ x is equal to $ y.
===	Equality (identical)	$ X ===$ y	Returns true if $ x is equal to $ y and has the same type.
! =	Not equal	$ X! = $ Y	Returns true if $ x is not equal to $ y.
<>	Not equal	$ X <> $ y	Returns true if $ x is not equal to $ y.
! =	Incomplete (completely different)	$ X! ==$ Y	If $ x is not equal to $ y and their types are different, true is returned.
>	Greater	$ X> $ y	If $ x is greater than $ y, true is returned.
<	Greater	$ X <$ y	If $ x is less than $ y, true is returned.
> =	Greater than or equal	$ X> = $ y	Returns true if $ x is greater than or equal to $ y.
<=	Less than or equal	$ X <= $ y	If $ x is less than or equal to $ y, true is returned.

Logical operators:

Operator	Name	Example	Result
And	And	$ X and $ y	If both $ x and $ y are true, true is returned.
Or	Or	$ X or $ y	If either $ x or $ y is true, true is returned.
Xor	Exclusive or	$ X xor $ y	If $ x and $ y have only one of them, true is returned.
&&	And	$ X & $ y	If both $ x and $ y are true, true is returned.
|	Or	$ X | $ y	If either $ x or $ y is true, true is returned.
!	Non	! $ X	Returns true if $ x is not true.

Array OPERATOR:

Operator	Name	Example	Result
+	Union	$ X + $ y	$ X and $ y (but do not overwrite duplicate keys)
=	Equal	$ X = $ y	Returns true if $ x and $ y have the same key/value pair.
===	Full	$ X ===$ y	True is returned if $ x and $ y have the same key/value pairs with the same sequence and type.
! =	Not equal	$ X! = $ Y	Returns true if $ x is not equal to $ y.
<>	Not equal	$ X <> $ y	Returns true if $ x is not equal to $ y.
! =	Incomplete	$ X! ==$ Y	Returns true if $ x is different from $ y.