Summary of the use of variable functions in php

PHP supports the concept of variable functions. This means that if there are parentheses after a variable name, PHP will look for a function with the same name as the variable's value and try to execute it. This article focuses on introducing you to a summary of the use of PHP variable functions. Friends who are interested should take a look at it

Variable functions

PHP supports variable functions concept. This means that if there are parentheses after a variable name, PHP will look for a function with the same name as the variable's value and try to execute it. Variable functions can be used to implement some purposes including callback functions and function tables.

Variable functions cannot be used in language structures such as echo(), print(), unset(), isset(), empty(), include(), require() and similar statements. You need to use your own wrapper functions to use these structures as variable functions.

Write my pseudocode first.

 protected $model;
 public function __construct(Category $category)
 {
  $this->model = $category;
 }
 public function getLists($request, $isPage = 'get', $order = 'created_at', $sort = 'desc')
 {
  return $this->model->orderBy($order, $sort)->$isPage();
 }

In getLists, there is a $isPage parameter. The original intention is to pass in get to get all the data, and paginate to paginate. After I finished writing, I felt something was wrong. In our usual way of writing, find all data $this->model->orderBy($order, $sort)->get(); This is like this, I have never seen it used Variables to replace get(). In actual operation, the program executes normally. Then asked about this writing method in the forum. Next, we will introduce a concept, "Variable Function".

What is a variable function?

PHP supports the concept of variadic functions. This means that if there are parentheses after a variable name, PHP will look for a function with the same name as the variable's value and try to execute it.

After understanding this concept, the above procedure will make sense. When the program is running, $isPage is replaced by get, and there is a parenthesis after $isPage, then the program will look for a function with the same name. Then continue execution.

Example:

<?php
function foo() {
 echo "In foo()<br />\n";
}
function bar($arg = '') {
 echo "In bar(); argument was '$arg'.<br />\n";
}
$func = 'foo';
$func();  // 执行 foo(); 命令行中输出：In foo()<br />
$func = 'bar';
$func('test'); // 执行 bar();命令行中输出：In bar(); argument was 'test'.<br />

Variable function syntax to call an object's method.

<?phpclass Foo
{
 function Variable()
 {
  $name = &#39;Bar&#39;;
  $this->$name(); // This calls the Bar() method
 }
 function Bar()
 {
  echo "This is Bar";
 }
}
$foo = new Foo();
$funcname = "Variable";
$foo->$funcname(); // This calls $foo->Variable()
// 命令行执行输出： This is Bar

When calling static methods, function calls take precedence over static properties. Variable methods and static properties examples.

<?php
class Foo
{
 static $variable = &#39;static property&#39;;
 static function Variable()
 {
  echo &#39;Method Variable called&#39;;
 }
}
echo Foo::$variable; // This prints &#39;static property&#39;. It does need a $variable in this scope.
$variable = "Variable";
Foo::$variable(); // This calls $foo->Variable() reading $variable in this scope.

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