Functions
PHP has hundreds of base functions and thousands more from extensions. Functions are not first-class functions and can only be referenced by their name prior to PHP version 5.3.0, whereas PHP 5.3.0 introduces closures. User-defined functions can be created at any time and without being prototyped. Functions can be defined inside code blocks, permitting a run-time decision as to whether or not a function should be defined. There is no concept of local functions. Function calls must use parentheses with the exception of zero argument class constructor functions called with the PHP new
operator, where parentheses are optional.
An example function definition is the following:
Prior to version 5.3, PHP only supports quasi-anonymous functions through the create_function
function. These are not true anonymous functions because anonymous functions are nameless but functions can only be referenced by name in PHP. As of version 5.3, PHP supports true anonymous functions.
Function calls may be made via variables, where the value of a variable contains the name of the function to call. This is illustrated in the following example:
PHP does not support named parameters or parameter skipping. Some core PHP developers have publicly expressed disappointment with this decision. Others have suggested workarounds for this limitation.
Read more about this topic: PHP Syntax And Semantics
Famous quotes containing the word functions:
“If photography is allowed to stand in for art in some of its functions it will soon supplant or corrupt it completely thanks to the natural support it will find in the stupidity of the multitude. It must return to its real task, which is to be the servant of the sciences and the arts, but the very humble servant, like printing and shorthand which have neither created nor supplanted literature.”
—Charles Baudelaire (18211867)
“Adolescents, for all their self-involvement, are emerging from the self-centeredness of childhood. Their perception of other people has more depth. They are better equipped at appreciating others reasons for action, or the basis of others emotions. But this maturity functions in a piecemeal fashion. They show more understanding of their friends, but not of their teachers.”
—Terri Apter (20th century)
“The mind is a finer body, and resumes its functions of feeding, digesting, absorbing, excluding, and generating, in a new and ethereal element. Here, in the brain, is all the process of alimentation repeated, in the acquiring, comparing, digesting, and assimilating of experience. Here again is the mystery of generation repeated.”
—Ralph Waldo Emerson (18031882)