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PHP has hundreds of base functions and thousands more from extensions. Prior to PHP version 5.3.0, functions are not first-class functions and can only be referenced by their name, whereas PHP 5.3.0 introduces closures. [35] User-defined functions can be created at any time and without being prototyped. [35]
It is impossible in general to distinguish between a function partly applied, and a function to which a subset of parameters have been provided. OCaml resolves this ambiguity by requiring a positional argument after all optional named-parameter arguments: its presence or absence is used to decide if the function has been fully or partly applied.
This has been supported for classes and interfaces since PHP 5.0, for arrays since PHP 5.1, for "callables" since PHP 5.4, and scalar (integer, float, string and boolean) types since PHP 7.0. [71] PHP 7.0 also has type declarations for function return types, expressed by placing the type name after the list of parameters, preceded by a colon ...
In case of call by value, what is passed to the function is the value of the argument – for example, f(2) and a = 2; f(a) are equivalent calls – while in call by reference, with a variable as argument, what is passed is a reference to that variable - even though the syntax for the function call could stay the same. [5]
When a member function is called on an object, it invokes the member function with the same name on the object's class object, with the object automatically bound to the first argument of the function. Thus, the obligatory first parameter of instance methods serves as this; this parameter is conventionally named self, but can be named anything.
In most programming languages, functions may take one or more arguments. Usually, each argument must be specified in full (this is the case in the C programming language [1]). Later languages (for example, in C++) allow the programmer to specify default arguments that always have a value, even if one is not specified when calling the function.
In PHP 5, a recommended name for a constructor is __construct. For backwards compatibility, a method with the same name as the class will be called if __construct method can not be found. Since PHP 5.3.3, this works only for non-namespaced classes. [1] In PHP 7, you should always name the constructor as __construct. Methods with the same name ...
PHP uses argc as a count of arguments and argv as an array containing the values of the arguments. [ 4 ] [ 5 ] To create an array from command-line arguments in the -foo:bar format, the following might be used: