What’s PHP Operator?

Programming languages typically support a few operators: constructs which behave generally like functions, but which differ syntactically or semantically from usual functions. Common simple for instance arithmetic (addition with +), comparison (with > ), and logical operations (such as AND or &&). More involved for instance assignment (usually = or :=), field access within an archive or object (usually .), and the scope resolution operator (often ::). Languages usually define a few built-in operators, as well as perhaps allow users to add new meanings to existing operators or even define new operators.

Source: PHP Operators

Syntax

Syntactically operators usually comparison to functions. For most languages, functions could possibly be seen as a special kind of prefix operator with fixed precedence level and associativity, often with compulsory parentheses e.g. Func(a) (or (Func a) in Lisp). Most languages support programmer-defined functions, but might not claim to aid programmer-defined operators, unless they have significantly more than prefix notation and greater than a single precedence level. Semantically operators is seen as special type of function with different calling notation and a restricted number of parameters (usually one or two 2).

The positioning of the operator regarding its operands could possibly be prefix, infix or postfix, and the syntax of a manifestation involving an operator is dependent upon its arity (number of operands), precedence, and (if applicable), associativity. Most programming languages support binary operators plus some unary operators, with a few supporting more operands, just like the ?: operator in C, which is ternary. There are prefix unary operators, such as unary minus -x, and postfix unary operators, such as post-increment x++; and binary operations are infix, such as x + y or x = y. Infix operations of higher arity require additional symbols, just like the ternary operator ?: in C, written as a ? b : c – certainly, this can be an only common example, it really is referred to as the ternary operator. Prefix and postfix operations can support any desired arity, however, such as 1 2 3 4 +.

Occasionally components of a language could possibly be known as “matchfix” or “circumfix” operators, either to simplify the language’s description or implementation. A circumfix operator includes a number of parts which enclose its operands. Circumfix operators possess the very best precedence, with their contents being evaluated and the resulting value within the encompassing expression. The most familiar circumfix operator would be the parentheses pointed out previously, used to point which elements of a manifestation ought to be evaluated before others. Another example from physics could be the inner product notation of Dirac’s bra-ket notation. Circumfix operators are specially good for denote operations that involve many or varying amounts of operands.

The specification of a language will specify the syntax the operators it supports, while languages such as Prolog that support programmer-defined operators require that the syntax be defined by the programmer.

Semantics

The semantics of operators particularly is dependent upon value, evaluation strategy, and argument passing mode (such as boolean short-circuiting). Simply, a manifestation involving an operator is evaluated for reasons uknown, and the resulting value could possibly be only a value (an r-value), or could possibly be an object allowing assignment (an l-value).

In simple cases that’s identical to usual function calls; for example, addition x + y is generally add up to a function call add(x, y) and less-than comparison x < y to lt(x, y), and then the arguments are evaluated of their usual way, then some function is evaluated and the result is returned as a value. However, the semantics could possibly be significantly different. For example, in assignment a = b the prospective an isn’t evaluated, but instead its location (address) may be used to store the worth of b – corresponding to call-by-reference semantics. Further, an assignment is actually a statement (no value), or is actually a manifestation (value), with the worth itself either an r-value (only a value) or an l-value (able to be assigned to). As another example, the scope resolution operator :: and the element access operator . (as in Foo::Bar or a.b) operate not on values, but on names, essentially call-by-name semantics, and their value is a name.

Using l-values as operator operands is specially notable in unary increment and decrement operators. In C, for instance, the pursuing statement is normally legal and well-defined, and is dependent upon the very fact that array indexing returns an l-value: