If you don't understand, why do parameters in methods like exec (), preg_match_all () have output without declaring variables?

for example: 

$str = "123123";
preg_match_all("/(\d*)/", $str, $arr);
var_dump($arr);

or: 

exec("date", $output);
var_dump($output);

this is not declared $output , and can be output as $arr ? What is the reason for this?

add 

<?php
var_dump($res);   // ,

//
function test(&$a){
        $aPP;
}

test($a);
echo $a;   //  1%
Php
May.12,2021

you can, too. 

function fun($a,&$b)
{
    $b = $a;
}
fun(1,$x);
var_dump($x);
Variables in

php do not need to be declared before use, and for output variables that pass addresses, initializes is not necessary if you do not use initial values.

see
http://php.net/manual/en/lang.

Previous: What is the number next to the intellij IDEA line number?

Next: Will gulp-cssnano delete the-webkit-box-orient: vertical; style?

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-64f5-1e50999-450e3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e50999-450e3.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?