The problem of PHP closure function

$name = function(){
    $a="x";
        $name2=function() use ($a){
        return "".$a;
        };
        return $name2;
};

echo $name () (); / / Why do I have to write two parentheses here to output?

Php
Jan.03,2022

because your above code uses two = function () {} , defining two nested closures. Isn't it reasonable to pair two closures with two parentheses.

nested closure. The return value of $name () is a closure function, and $name () () is the inner closure of the call

. The

function is also a value, an object, like 123,1.341, "str", which is not difficult.

$name is a function: 

function(){
$a="x";
    $name2=function() use ($a){
    return "".$a;
    };
    return $name2;
};

$name () is the return value of $name for this function (above function) (that is, the internally returned function $name2): 

function() use ($a){
        return "".$a;
        };

$name () () is the call to the internal $name2 corresponding function. The result, of course, is the return value of this statement return "I like to eat". $a;

There is no doubt that

calls $name this closure function requires the use of $name () .

but what is the value returned by $name () ? $name2 is returned, while $name2 is a closure function, while calling $name2 requires $name2 () .

so echo $name () () is equivalent to: 

  
 because the return value is a method

Previous: Vue-quill-editor Rich text Editor Echo does not display spaces problem

Next: If webpack3 uses url-loader and does not install file-loader, it will report an error.

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1eb2dd1-481cf.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1eb2dd1-481cf.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?