Complete knowledge about PHP operators_PHP tutorial-PHP Tutorial-php.cn

It seems to be a simple thing, but in actual application, it is still very interesting

Arithmetic operator
Operator name result
$a + $b Add $a and $ Sum of b
$a - $b Subtraction Difference of $a and $b
$a * $b Multiplication Product of $a and $b
$a / $b Division $a divided by $b Quotient
$a % $b Modulo $a divided by $b remainder , and then perform the operation
$a++, then add the value of $a, perform the operation first, then add one
--$a　, then subtract the value of $a by one, and then perform the operation
$a--　The value of $a is first operated and then reduced by one
Example:

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The code is as follows:< ?php

echo $a=5+”5th”; //Output: 10

echo 10%3; //Output: 1 
echo 10+ $a++; //Output: 20 
 echo 5- --$a; //Output: -5 
?> 



Comparison operator

Operator name result$a == $b equals TRUE if $a equals $b $a === $b is congruent TRUE if $a equals $b and they are of the same type
$a != $b No equal to TRUE if $a is not equal to $b
$a <> $b is not equal to TRUE if $a is not equal to $b
$a !== $b is not equal to TRUE if $a Not equal to $b, or they are of different types
$a < $b is less than TRUE if $a is strictly less than $b
$a > $b is greater than TRUE if $a is strictly $b
$a <= $b is less than or equal to TRUE if $a is less than or equal to $b
$a >= $b is greater than or equal to TRUE if $a is greater than or equal to $b
Another conditional operator is " ? : " (or ternary) operator.
Example:

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The code is as follows:var_dump(0==" a"); //Output: bool(true)

var_dump(0=="00"); //Output: bool(true) 
var_dump(0==="00"); //Output ：bool(false) 
var_dump(0<>"abc"); //Output: bool(false) 
var_dump(0!=="01"); //Output: bool(true) 
$a=10; 
$b=20; 
$str=$a>$b? "true":"false"; 
echo $str; //Output: false 
 ?> 



Logical Operator

Operator Name Result$a and $b Logical AND TRUE, if both $a and $b are TRUE. $a or $b Logical OR TRUE if either $a or $b is TRUE.
$a xor $b XOR TRUE if $a and $b are different at the same time
! $a logically not TRUE if $a is not TRUE.
$a && $b logical AND TRUE if both $a and $b are TRUE.
$a || $b logical OR TRUE if either $a or $b is TRUE.
Among them, and and &&, or and || are two ways of writing the same logical operator.
Logical AND and Logical OR are both short-circuit operators. When encountering the following logical expression, the PHP interpreter will not evaluate the expression on the right:

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The code is as follows: $a=10;

if(false && (++$a)); 
echo $a; //Output: 10 
$b=10; 
if(true or (++$b)); 
echo $b; //Output: 10 
?>

 

bit operator

Bitwise operators allow setting specified bits in integers. If both left and right arguments are strings, the bitwise operators operate on the ASCII values of the characters. Expression Name Result $a & $b bitwise AND will set the bits in $a and $b that are both 1 to 1.
$a | $b bitwise OR will set the bit in $a or $b that is 1 to 1.
$a ^ $b bitwise XOR will set different bits in $a and $b to 1.
~ $a Bitwise NOT Sets bits in $a that are 0 to 1, and vice versa.
$a << $b left shift Moves the bits in $a to the left $b times (each move means "multiply by 2").
$a >> $b right shift Move the bits in $a to the right $b times (each move means "divide by 2").
Other operators

String operators

There are two string operators. The first is the concatenation operator ("."), which returns the concatenated string of its left and right arguments. The second is the concatenation assignment operator (".="), which appends the right argument to the left argument. Error suppression operator
In the most common database connection and file creation operations or when exceptions such as division by 0 occur, the @ symbol can be used to suppress the output of function error information to the browser $a=@(5/0 ) External command execution
Use `` to run external system commands. Note that it is not a single quote, but the key under ESC

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Code As follows: $out=`dir c:`;

print_r($out); 
?>//It is not recommended to use 
 

Example: 

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The code is as follows:

$a="hello"; 
$a.=" world! "; //Equivalent to: $a=$a." world!"; 
echo $a; //Output: hello world! 
$m = 3; 
$m += 5; //Equivalent to: $m=$m+5; 
echo $m; / /Output: 8 
$c = ($b = 4) + 5; 
echo $c; //Output: 9 
?>

Operation Operator precedence
The following table lists the precedence of operators from low to high.
Combined direction operators
left,
left or
left xor
left and
right print
right= += -= *= /= .= %= & = |= ^= ~= <<= >>=
left? :
left||
left&&
combined with direction operator
left|
left ^
Left&
None== != === !==
None< <= > >=
Left<< >>
Left + - .
left* / %
right! ~ ++ -- (int) (float) (string) (array) (object) @
right[
none new

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