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One of the most important tools in any programming language are the functions. A function is a set of routines and actions throughout the script will be executed multiple times grouped in a function and from anywhere in the script can be called and executed. In turn, this function can take external parameters of which depend on the result of a function. The functions should always be placed before the function call (of course). The function syntax is as follows: function name (parameters) { function instructions } to call the function would be as follows: name (parameters) An example to understand the use of functions is as follows: We will create a function that performs the sum of two numbers and display the result function add ($ sumando1, $ sumando2) { $ Sum = $ sumando1 + $ sumando2 echo $ sumando1 ."+".$ ."=".$ sumando2 sum; } sum (5.6) An important fact to note is that the variables declared within the function or will only exist this value within the function. There are cases where we do not know the number of parameters you pass to the function and in these cases we use the functions created for this purpose as: func_num_args () Number of parameters that have been passed to the function func_get_args () Returns an element that form the argument list |
Introduction
This would be a call to a function without parameters:<? Php
function Hello () {
$ Message = "Hello friend";
echo $ message;
}
?>
<html>
<head>
<title> My Page </ title>
</ Head>
<body>
<? Php
Hello ();
?>
</ Body>
</ Html>
Hello (), Which will print the text "Hello friend."
Functions with parameters.
If you need a function to which you can pass parameters, be written in the same way, with the name of the parameters between the parentheses, separated by commas. For a two-parameter function, the code might look something like:
<? Php
function sum ($ a, $ b) {
return $ a + $ b;
}
$ A = 1, $ b = 2;
echo "Let's add $ a + $ b =". sum ($ a, $ b);
?>
Note that in this example we use the keyword return. This word is used for function return values to the place where it was called.
For practical purposes we say that the function is executed in a separate and "replaced" at runtime by the result returned by return in the context in which they had called. In the above example, add ($ a, $ b) === 3 (being the identity operator ===).
Default Parameters
In the formal definition of the function can specify default settings, so that if one is not passed at the time of call, the parameter takes a value. If this value is not specified, the interpreter will return a runtime error for invalid number of parameters.To specify, here's how:
Example of default
function test ($ foo = 'bar') {
/ * Operations * /
return $ foo
}
Function Overloading
From PHP4 [Note 1] , functions can be overloaded, ie, define functions that accept parameters and can have a different internal logic.An overloaded function can be something like:
First attempt
overload function () {
return array (1);
}
overload function ($ a) {
return array (2, $ a);
}
overload function ($ a, $ b) {
return array (3, array ($ a, $ b));
}
Ovelar function ($ a, $ b, $ c) {
return array (4, array ($ a, $ b, $ c));
}
Needless to say, since PHP5 [Note 1] functions with no parameters specified (with an empty list) can receive any number of arbitrary parameters. The list of functions above could be rewritten as one, as follows:
Best approximationfunc_num_args () PHP Manual ,
func_get_args () PHP Manual
not_overloaded function () {
return array (
func_get_args () PHP Manual
);
}
An example shows the parameters used, typically in the books, is as follows:
function abc
function abc () {
$ Array = func_get_args ();
$ ArrayCount = count ($ array);
for ($ i = 0; $ i <$ arrayCount, $ i + +) {
echo "$ i used as a parameter: {$ array [$ i]}";
}
}
Abc function callResult
abc ('test', 'test2', 3, 4);
Was used as a parameter 0: test
Was used as parameter 1: test2
Was used as parameter 2: 3
Was used as parameter 3: 4
You can also create anonymous functions at runtime. These functions are very useful in the lambda-calculus, and are created with create_function PHP-Manual , with a string in the second parameter would be the PHP code must perform the function. In PHP6 will introduce a new style of anonymous functions that also allows to assign functions to variables, as well as in other languages such as JavaScript.
Thus, the following code would be valid in PHP6 or higher.
Experimental code
$ A = function ($ b) {return $ b;};
if ($ a (45) == 45) echo "Good!" / / It prints 'OK!'
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