An operator is something that takes one or more values (or expressions, in programming jargon) and yields another value (so that the construction itself becomes an expression).
Operators can be grouped according to the number of values they take. Unary
operators take only one value, for example
logical not operator) or
Binary operators take two values, such as the familiar
+ (plus) and
- (minus), and the
majority of PHP operators fall into this category. Finally, there is a
? :, which takes three values; this is
usually referred to simply as "the ternary operator" (although it could
perhaps more properly be called the conditional operator).
A full list of PHP operators follows in the section Operator Precedence. The section also explains operator precedence and associativity, which govern exactly how expressions containing several different operators are evaluated.