The explanation of variable parameter function and optional parameter function in PHP

1) optional parametric function. For example:

<?phpfunction Add ($var 1, $var 2, $var 3=0, $var 4=0) {     return $var 1+ $var $var $var 4;} echo Add (+);    Output 2echo Add (1,1,1); Output 3echo Add (1,1,1,1);//Output 4echo Add (1);      Error: Must give parameter 2echo Add (1,1,,1);//Error: Cannot omit an optional parameter and give the last optional parameter in the list?>

Because $var3 and $VAR4 are given default values in defining functions, if they are not passed to them, they are the default values, and all are optional.

2) variable parameter function

<?php     function variable ()         {                  echo Func_num_args ();         Number of output parameters                  $varArray = Func_get_args;     Gets the parameter array, which returns the Echo $value of the parameter arrays                   foreach ($varArray as $value)                     ;                                       echo Func_get_arg;       Get a single parameter                            }?>