PHP Operators

An operator is a special symbol that carries out an action on variables and values, such as adding two numbers or comparing them.

PHP's operators fall into these groups:

• Arithmetic operators
• Assignment operators
• Comparison operators
• Increment/Decrement operators
• Logical operators
• String operators
• Array operators
• Conditional assignment operators

These are the operators you know from math class. They work on numeric values and handle everyday calculations like adding, subtracting and multiplying.

The list below shows each one and what it produces:

• + Addition - $x and $y added together
• - Subtraction - $y taken away from $x
• * Multiplication - $x times $y
• / Division - $x divided by $y
• % Modulus - What is left over after dividing $x by $y
• ** Exponentiation - $x raised to the power of $y

An assignment operator writes a value into a variable, and the ones below are used with numeric values.

The simplest is =, which gives the variable on its left the value of the expression on its right. The others are shorthand for doing a calculation and storing the result in one step:

• x = y means x takes the value of y, with no shorthand involved
• x += y does the same job as x = x + y
• x -= y does the same job as x = x - y
• x *= y does the same job as x = x * y
• x /= y does the same job as x = x / y
• x %= y does the same job as x = x % y

Comparison operators look at two values, either numbers or strings, and tell you how they relate.

• == Equal - Gives true when $x and $y have the same value
• === Identical - Gives true only when $x and $y have the same value and also the same type
• != Not equal - Gives true when the values of $x and $y differ
• <> Not equal - Another way of writing !=, with the same result
• !== Not identical - Gives true when $x and $y differ in value or in type
• > Greater than - Gives true when $x is larger than $y
• < Less than - Gives true when $x is smaller than $y
• >= Greater than or equal to - Gives true when $x is larger than $y or the two are equal
• <= Less than or equal to - Gives true when $x is smaller than $y or the two are equal
• <=> Spaceship - Gives an integer: below zero when $x is the smaller value, zero when they are equal, and above zero when $x is the larger value

Increment operators raise a variable's value by one, and decrement operators lower it by one. Where the operator sits matters: in front of the variable, the change happens before the value is returned; behind it, the change happens afterwards.

• ++$x Pre-increment - Adds one to $x first, then returns the new value
• $x++ Post-increment - Returns the current value of $x, then adds one
• --$x Pre-decrement - Subtracts one from $x first, then returns the new value
• $x-- Post-decrement - Returns the current value of $x, then subtracts one

Logical operators let you join conditions together into a single test.

• and - True when both conditions hold
• or - True when at least one condition holds
• xor - True when exactly one condition holds, never both
• && - True when both conditions hold (same as and)
• || - True when at least one condition holds (same as or)
• ! - True when the condition is false

Two operators exist just for working with strings.

• . Concatenation - Joins two strings into one
• .= Concatenation assignment - Adds one string onto the end of another

Here the . operator joins $txt1 and $txt2, and echo prints the combined text:

Here .= adds more text to the end of $txt1, changing the variable itself:

These operators work on whole arrays, mostly to compare one with another.

• + Union - Combines $x and $y into their union
• == Equality - Gives true when both arrays hold the same key/value pairs
• === Identity - Gives true when both arrays hold the same key/value pairs, in the same order and with the same types
• != Inequality - Gives true when $x and $y aren't equal
• <> Inequality - Another way of writing !=, with the same result
• !== Non-identity - Gives true when $x and $y aren't identical

Conditional assignment operators choose a value based on a condition.

• ?: Ternary - In $x = expr1 ? expr2 : expr3, $x receives expr2 when expr1 is true and expr3 when it is false
• ?? Null coalescing - In $x = expr1 ?? expr2, $x receives expr1 as long as it exists and isn't NULL; if it is missing or NULL, $x receives expr2

The condition here checks whether $x divides evenly by 2. It does, so the ternary operator picks its first value, "Even":

?? hands back its first operand when that operand exists and isn't NULL, and its second operand otherwise. Since $color doesn't exist here, the result falls back to "red":