3.5. PHP Operators
Operators are used for performing specific tasks. The operators in PHP are same like other programming languages like Arithmetic operators, Assignment Operators, Comparison Operators, and logical operators.
3.5.1. Arithmetic Operators
These operators work similar to basic Mathematics functions.
Example 
Name 
Result 
$a + $b 
Addition 
Sum of $a and $b. 
$a  $b 
Subtraction 
Difference of $a and $b. 
$a * $b 
Multiplication 
Product of $a and $b. 
$a / $b 
Division 
Quotient of $a and $b. 
$a % $b 
Modulus 
Remainder of $a divided by $b. 
Like other programming language, in PHP too, logical operators are used to compare elements, but the syntax is different like:
Example 
Name 
Result 
$a and $b 
And 
TRUE if both $a and $b are TRUE. 
$a or $b 
Or 
TRUE if either $a or $b is TRUE. 
$a xor $b 
Xor 
TRUE if either $a or $b is TRUE, but not both. 
! $a 
Not 
TRUE if $a is not TRUE. 
$a && $b 
And 
TRUE if both $a and $b are TRUE. 
$a  $b 
Or 
TRUE if either $a or $b is TRUE. 
These give you the ability to compare whether elements are equal, identical, less than or greater than one another (with some other variations).
Example 
Name 
Result 
$a == $b 
Equal 
TRUE if $a is equal to $b. 
$a === $b 
Identical 
TRUE if $a is equal to $b, and they are of the same type. (PHP 4 only) 
$a != $b 
Not equal 
TRUE if $a is not equal to $b. 
$a <> $b 
Not equal 
TRUE if $a is not equal to $b. 
$a !== $b 
Not identical 
TRUE if $a is not equal to $b, or they are not of the same type. (PHP 4 only) 
$a < $b 
Less than 
TRUE if $a is strictly less than $b. 
$a > $b 
Greater than 
TRUE if $a is strictly greater than $b. 
$a <= $b 
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. 

Recommend the tutorial 