PHP learning operators and operator precedence_PHP tutorial-PHP Tutorial-php.cn

PHP learning operators and operator precedence_PHP tutorial

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Release： 2016-07-21 15:51:51

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Arithmetic operator
Operator Name Result
$a + $b Addition Sum of $a and $b
$a - $b Subtraction Difference of $a and $b
$a * $b Multiplication The product of $a and $b
$a / $b Division Division The quotient of $a divided by $b
$a % $b Modulo The remainder of $a divided by $b
Increasing/decreasing operations Symbol
Operator Name Result
++$a Add the value of $a before adding one, then perform the operation
$a++ Add after the value of $a Operate first, then add one
-- $a 　 Front minus The value of $a is decremented by one, and then the operation is performed
$a-- Post-decrement The value of $a is operated first, and then decremented by one
Example:
echo $a=5+”5th”; //Output: 10
echo 10%3; //Output: 1
echo 10+ $a++; //Output: 20
echo 5- --$ a; // Output: -5 === $ B Full True, if $ a is equal to $ B, and their types are the same
$ a! = $ B, which is not waiting for TRUE, if $ a is not equal to $ b
$ a & lt; & gt; & gt; & gt; & gt ; $b is not equal TRUE if $a is not equal to $b
$a !== $b Not congruent TRUE if $a is 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 Greater than or equal to TRUE if $a is greater than or equal to $b
Another conditional operator is the " ? : " (or ternary) operator.

Example:
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 $a and $b are both 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 Logical NOT TRUE if $a is not TRUE.
$a && $b Logical AND TRUE, if $a and $b are both TRUE.
$a || $b Logical OR TRUE, if either $a or $b is TRUE.

Where 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 expressions, the PHP interpreter will not evaluate the expression on the right:
$a=10;
if(false && (++$a)) ;
echo $a; //Output: 10
$b=10;
if(true or (++$b));
echo $b; //Output: 10
?>
Bitwise Operators
Bitwise operators allow setting specified bits in integers. If the left and right arguments are both strings, the bitwise operators will operate on the ASCII values of the characters.
Expression Name Result
The bitwise AND of $a & $b 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 the 0 bits in $a to 1, and vice versa.
$a << $b Shift Left 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 $a=@(5/0 )
External command execution
Use `` to run external system commands. Note that it is not a single quote, but the key under ESC
> print_r($out); "; //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
?>
Operator precedence
The following table lists the precedence of operators from low to high.
Combining direction operators
left ,
left or
left xor
left and
right print
right = += -= *= /= .= %= & = |= ^=
Left |
Left ^
Left &
None == != === !==
None < <= > >=
Left << >>
Left + - .
Left * / %
Right ! ~ ++ -- (int) (float) (string) (array) (object) @
Right [
None new

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