How are the PHP operators categorized according to different criteria?

Classification of operators:

The PHP operator can be divided into unary operators, two-ary operators, and ternary operators based on the number of operands. Unary operators such as ! (take the inverse operator) or ++ (plus an operator), most of the operators supported by PHP are such binary operators, such as,, + , and - * / so on, while the ternary operator has only one ( ?: ). In addition, by the function of the operator to classify, can be divided into: arithmetic operators, string operators, assignment operators, comparison operators, logical operators, bitwise operators and other operators.

1. Arithmetic operators

Operator	Meaning	Writing format
+	Addition operation	$a + $b
-	Subtraction operations	$a-$b
*	Multiplication operations	$a * $b
/	Division operation	$a/$b
%	Take Division remainder operation	$a% $b
++	Since the increase of 1, such as $a++, is actually $a= $a +1	$a + +
--	Self minus 1, for example $ A--, is actually $a= $a-1	$a--

In the arithmetic operator, there is an increment and decrement rule that almost all programs have, as follows:

• $a++Evaluates the value of the expression first and then adds 1 to itself

• $a--The value of the expression is evaluated first, and then the self is reduced by 1

• ++$aAdd 1 First, and then calculate the value of the expression

• --$aSubtract 1 First, then calculate the value of the expression

Instance:

<?php    $count =1;    echo $count + +;  This line prints out 1    echo + + $count;  This line prints out the 3?>

2. String operators

In PHP, there is only one string operator, which is an English period ("."), also known as a join operator. This operator can not only concatenate two strings into a new merged string, but also concatenate a string with any scalar data type and merge it into a new string.

<?php$name = "Kevin";                Define a person's name as a string type $age = x;                      Define a person's age as integral type $height = 1.85;                 Define a person's height as floating-point type//Use the dot operator and string to concatenate the variables above, and output echo "My name is:". $name. ", My Age is:". $age. ", my height." $height. " Meters. "." <br> ";? >

3. Assignment operators

• =Assigns the result of a value or expression to a variable

• +=The result of adding the variable to the assigned value is then assigned to the variable

• -=Assigns the result to the variable that subtracts the most from the assigned value

• *=Assigns the result to the variable that is the most multiplied by the assigned value.

• /=Assigns the result that divides the most to the assigned value to the variable

• %=Assigns the result of the variable that divides the most to the assigned value to the

• .=Assigns the result to the variable that is most connected to the assigned value

<?php $a = $b = $c = $d =;            The values for $a, $b, $c, and $d are 20$a + = 5;                      Equivalent to $a = $a +5; $b-= 5;                      Equivalent to $b = $b-5; $c *= 5;                      Equivalent to $c = $c; $d/= 5;                      Equivalent to $d = $d/5; $e%= 5;                      Equivalent to $e = $e%5; $result = "The result is:"; $result. = "\ $a the value after 5 is: ${a},"; $result. = "\ $b self-minus 5 after the value is: ${b},"; $result. = "\ $c squared 5 After the value is: ${ c}, "; $result. =" \ $d since the value after 5 is: ${d}, "; $result. =" \ $e The value after 5 fetch is: ${e}. "; Echo $result;                       Output of all concatenated string results?>

4. Comparison operators

• ; is greater than, returns TRUE when the left operand is greater than the right operand. Otherwise, FALSE

• < is less than, and returns TRUE when the left operand is less than the right-hand operand. Otherwise FALSE

• >= is greater than or equal, and returns TRUE when the left operand is greater than or equal to the right operand. Otherwise FALSE

• <= is less than or equal, and returns TRUE when the left operand is less than or equal to the right operand. Otherwise FALSE

• = = equals, returns TRUE when the left operand equals the right operand. Otherwise FALSE

• = = = all equals, when the left operand equals to the right operand, and their type also returns TRUE . Otherwise FALSE

• <> or ! = is not equal to return TRUE when the left operand is not equal to the right operand . Otherwise FALSE

• !== is not equal to return TRUE when the left operand is not equal to the right operand or the two types are unequal. Otherwise returns FALSE

<?php $a =1;                           Declares an integer variable $ A value of 1var_dump ($a > 1);              The result of the comparison is bool (false), 1 less than 1var_dump ($a < true);          The result of the comparison is bool (false), and the ture will automatically convert to 1var_dump ($a >= 0.01);         The result of the comparison is bool (true), 1 greater than 0.01var_dump ($a <= "0.10yuan");   The result of comparison is bool (false), "0.10yuan" will automatically turn to 0.10 and then compare var_dump ($a = = 1);            The result of the comparison is bool (true), 1 equals 1var_dump ($a = = "1");          The result of the comparison is bool (true), and "1" is automatically converted to 1 for comparison, equal to var_dump ($a = = = "1");         The result of the comparison is bool (false), although the content is the same, but not the same type of value var_dump ($a = = = 1);           The result of the comparison is bool (true), the content is the same, and the type is the same var_dump ($a <> 1);            The result of the comparison is bool (false), 1 equals 1, so it is false var_dump ($a! = 1);            The result of the comparison is bool (false), Ibid. var_dump ($a! = 0);            The result of the comparison is bool (true), and 1 is not equal to 0var_dump ($a!== "1");         The result of the comparison is bool (true), although the content is the same, but the type is different?>

5. Logical operators

PHP provides 4 logical operators: Logical AND ( and or && ), logical OR ( or or || ), logical non-( not or ! ), and XOR ( xor ).

• Logic and: The relationship between the logic and the expression "and", both sides of the expressions must be TRUE , the result can be true, otherwise the entire expression is false.

• Logical OR: A relationship that is logical or represents "or", where the expression on either side is one TRUE , the result is true, or the entire expression is false.

• Logical non: logical non-representation of the "inverse" relationship, if the expression is TRUE , the result becomes FALSE , if the expression is FALSE , the result is TRUE .

• Logical XOR: A logical XOR or an expression on both sides of an operation is not at the same time, that is TRUE TRUE , it must be one side of true and the other FALSE . Both sides of the expression at the same time, whether it is TRUE or both FALSE , the result is FALSE .

$username = "Apple";                Save the user name Apple in the variable $username $password = "123456";               Save the user password 123456 in the variable $password, "apple@163.com";       Save User e-mail apple@163.com in variable  $phone = "400-7654321";             Save user phone 400-7654321 in variable $phone    //Use a "logical and" operator, and a comparison operator together to determine if ($username = = "Apple" && $password = = "123456") {           echo "username and password entered correctly";}    Use a multiple "logical or" operator, together with a comparison operator, to determine if ($username = = "" "| | $password = = "" | | $email = = "" | | $phone = = "") {           echo "All values cannot be empty";}    Multiple different logical operators are mixed and used together with the return Boolean function as a condition to determine if (Isset ($email) &&!empty ($email)) | | (Isset ($phone) &&!empty ($phone))) {           echo "at least one contact method";}

6. Ternary operators

?:can provide a simple logical judgment, in PHP, the ternary operator in this one root only one. is equivalent to a conditional statement if...else... . Its syntax format is as follows: (exprl)? (expr2)：(expr3) . The meaning is that exprl when evaluated, it TRUE executes ? and : expr2 gets its value, exprl FALSE when evaluated, after it executes : expr3 and gets its value.

<?php     $money =100;    $result = $money >200? " "Good money": "no money spent";        Output no money spent the    echo $result; >