operators in php

1. Arithmetic operators

+ (Add) $a + $b
- (Subtract) $a - $b
* (Multiple) $a * $b
/(Divide) $a / $b
% (Remainder) $ a % $b

2. String operators

. (dot) (the only string operator in php)

3. Assignment operator
1. Simple assignment operator

= (equal sign)

2. Compound assignment operator

+= $a += $b is equivalent to $a = $a + $b
-= $a -= $b is equivalent to $a = $a - $b
*= $a *= $b is equivalent to $a = $a * $b
/+ $a /= $b is equivalent to $a = $a / $b
%= $a %= $b is equivalent to $a = $a % $b
.= $a .= $b is equivalent to $a = $a . $b

3. Pre-increment and decrement operations and post-increment and decrement operations

$a++ The value of $a itself has not changed, but the value of the entire expression will become $a + 1
++$a The value of $a itself has changed, $a is first replaced by $a = $a + 1, and then return $a + 1
$a-- The value of $a itself has not changed, but the value of the entire expression will become $a - 1
--$a The value of $a itself has changed, $a First $a = $a - 1, then return $a + 1

4. Reference operator

&

The reference operator & can be used in associative assignment. Usually, when assigning the value of one variable to another variable, a copy of the metavariable is first made and then stored elsewhere in memory. For example:

$a = 5;
$b = $a;

In the above example, the first line of code assigns a value to $a; the second line of code first generates a copy of $a and then saves it in $b. If the value of $a is subsequently changed, the value of $b will not change. Looking at the example below:

$a = 5;
$b = &$a;
$a = 7; // $a and $b are now both 7

Note: The reference is not an independent second pointer, but a pointer using the original variable, that is, both $a and $b point to the same address in the memory. In the above example, the second line is $a referenced by $b. When the value of $a in the third line changes, the $b that referenced it also changes. We can break this reference association by resetting:

unsert($a);

Note: This reset only resets $a, it does not change the value of $b(7). unsert($a) only destroys the association between $a and the value 7 stored in memory. Unsert($a) can be understood as canceling $a.

4. Comparison operators
Comparison operators return logical Boolean values: true or false.

==(equal to)
===(constantly equal to)
!=(not equal to)
!==(not equal to)
<>(not equal to)
<(less than)
> ;(greater than)
<==(less than or equal to)
>==(greater than or equal to)

5. Logical operators

! (Not)
&& (AND)
|| (OR)
and (AND)
or (OR)
xor (XOR) $a xor $b If $a or $b is true, then Return true. If $a and $b are both true or both false, return false.

Note: and and or have lower priority than && and ||.

6. Bit operators
Bit operators can treat an integer variable as a sequence of bits (Bits). Bitwise operators are not used often.

& (bitwise AND) $a & $b The result of ANDing each bit of $a and $b
| (bitwise OR) $a | $b The result of ANDing each bit of $a and $b The result obtained by performing the "OR" operation on each bit of b
~ (bitwise NOT) ~$a The result obtained by performing the "NOT" operation on each bit of $a
^ (bitwise XOR) $a ^ $ b The result of performing the "XOR" operation on each bit of $a and $b
<< (left shift) $a << $b Shift $a to the left by $b bits
>> (right shift) $a >> $b Shift $a right by $b

7. Other operators

, (comma) is used to separate function parameters or other list items. This operator is often used incidentally (not independently).
new (initializing an instance of a class)
-> (accessing members of a class)

1. Ternary operator?:

condition ? value if true : value if false

The ternary operator can be seen as the abbreviation of if else conditional statement.
2. Error suppression operator

@(at symbol)

The error suppression operator @ can be used before any expression, that is, before any expression that has a value or can be calculated, for example:

$a = @(57 / 0);

If the error suppression operator @ is not used in the above example, then this line of code will throw a divide-by-0 warning. If @ is used, the warning will be suppressed, that is, not thrown.
If some warnings are suppressed through this method and a warning is encountered, it needs to be handled through the error handling statements we have written in advance.
If the track_errors feature in php.ini is enabled, error messages will be stored in the global variable $php_errormsg.
3. Execution operator

`` (a pair of back single quotes) The execution operator is actually a pair of operators, a pair of back single quotes.

php will try to execute commands between back single quotes as server-side commands. The value of the expression is the result of the command execution. For example, in a unix system, you can use:

$out = `ls -la`;
echo ' ' . $out . ' ';

On Windows server, you can use:

$out = `dir c:`;
echo ' ' . $out . ' ';

In both cases, a directory list will be obtained and the list will be saved in $out. Then, the list will be displayed in the browser or processed by other methods.
4. Array operators
Note: In the syntax description below, $a and $b are not ordinary scalar values, but array types

+ (Union) $a + $b Returns an array containing all elements in $a and $b
== (Equivalent) $ == $b if $a and $b have the same key value Yes, return true
=== (identity) $a === $b If $a and $b have the same key-value pair and the same order, return true
!= (non-equivalence) $a != $b If $a and $b are not equivalent, return true
<> (not equivalent) $a <> $b If $a and $b are not equivalent, return true
!== (Non-Identity) $ !== $b If $a and $b are not identical, return true

5. Type operator
instanceof (the only type operator), this operator is used in object-oriented programming.
The instanceof operator allows checking whether an object is an instance of a specific class. For example:

class sampleClass();
$myObject = new sampleClass();
if ($myObject instanceof sampleClass) {
 echo 'myObject is an instance of sampleClass';
}
?>

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