Operators in php

In simple definition an operator is something that takes one or more values and generates another value. Operators can be of three types.

1)Unary Operator: Which operates on just one value. Like incremental operator (++) or negation operator(!).

2)Binary Operator: Which operates on two values. In php most of the operators are binary operators. Like +, -, * etc.

3)Ternary Operator: Which operators on three values. Example is ? : combination.
like, the expression (expr1) ? (expr2) : (expr3) evaluates to expr2 if expr1 evaluates to TRUE, and expr3 if expr1 evaluates to FALSE.

Based on the operator functionality it can be categorized into following:
1) Arithmetic Operators: Some basic arithmetic operator falls within this category.
Examples are -(negation -$a), +(addition $a+$b), -(subtraction $a-$b), * (multiplication $a*$b), division ($a/$b), modulus ($a%$b) where a and b are both variable. Note that Remainder $a % $b is negative for negative $a.

2) Assignment Operators: The = (equal sign) is the basic assignment operator. Whenever you write $a=$b it mean value of right hand variable b(operand) will be assigned to the left hand variable a.

3) Bitwise Operators: There are several bitwise operator that operates bit by bit between operands. These operators are below and beside the operator is the result.

& (bitwise AND - bit is set if both operands are set)
| (bitwise OR - bit is set if any of the operand is set)
^ (bitwise XOR - bit is set if bit is set in either of the operands but not when both are set)
~ (NOT) - bit is set if it is not set in the operator and vice-versa.
<< (Shift Left) - &a<<&b means shifts the bit of $a by $b steps to the left. >> (Shift Right) - &a>>&b means shifts the bit of $a by $b steps to the right.

4) Comparison Operators: Comparison operators are for comparing between two values. They returns boolean value.
Examples are,
== ($a==$b returns true if $a is equal to $b)
=== ($a===$b returns true if $a is equal to $b and $a has the same datatype as of $b)
!= or <> ( $a!=$b or $a<>$b will return true if $a is not equal to $b)
!==($ a!== $b will return true if $a is not equal to $b, or they are not of the same type.
< ($a < $b will return true if $a is less than $b.) > ($a > $b will return true if $a is strictly greater than $b.)
<= ($a <= $b will return true if $a is less than or equal to $b.) >= ($a >= $b will return true if $a is greater than or equal to $b.

5) Error Control Operators: The @ (at sign) is error control operator in php. If @ is prepend to variables, function, include() calls, constants then any error messages that might be generated by that expression will be ignored.

If the track_errors feature is enabled- which can be enabled by setting TRACK_ERRORS, any error message generated by the expression will be saved in the variable $php_errormsg. This variable will be overwritten on each error occurs.

6) Execution Operators: With php OS command can by executed by execution operator. If the commands are within backticks (` `) then PHP will attempt to execute the contents of the backticks as a shell command. Example is echo `ls -l`.

The backtick operator is disabled when safe mode (safe_mode =ON) is enabled or shell_exec() is disabled.

7) Incrementing/Decrementing Operators: Four incremental/decremental operators there.
++$a : Increments $a by one, then returns $a.
$a++ : Returns $a, then increments $a by one.
--$a : Decrements $a by one, then returns $a.
$a-- : Returns $a, then decrements $a by one.

8) Logical Operators:
AND : $a and $b becomes TRUE if both $a and $b are TRUE.
OR : $a or $b becomes TRUE if either $a or $b is TRUE.
XOR : $a xor $b becomes TRUE if either $a or $b is TRUE, but not both.
! : ! $a becomes TRUE if $a is not TRUE.
&& : $a && $b becomes TRUE if both $a and $b are TRUE.
|| : $a || $b becomes TRUE if either $a or $b is TRUE.

9) String Operators: One string type operation is concatenation(.) operator that concatenate it's left and right arguments. Another one is concatenating assignment operator ('.='), which appends the argument on the right side to the argument on the left side.

10) Array Operators: They work on array and examples are +,==,===, !=, <>,!== .

11) Type Operators: Example is, instanceof - which can be used to determine whether a variable is an instantiated object of a class.