Explanation of variable parameter functions and optional parameter functions in php

1) Optional parameters Function . For example:

<?php
function add($var1,$var2,$var3=0,$var4=0)
{
     return $var1+$var2+$var3+$var4;
}
echo add(1,1);    //输出2
echo add(1,1,1); //输出3
echo add(1,1,1,1);//输出4
echo add(1);      //出错:必须给出参数2
echo add(1,1,,1);//出错:不能漏掉一个可选参数而给出列表中最后一个可选参数
?>

Because $var3 and $var4 are given default values ​​in defining the function , if not Pass values ​​to them, that is, use default values, all are optional.

2)Variable parametersFunction

<?php
     function variable()
         {
                  echo func_num_args();         //输出参数个数
                  $varArray = func_get_args;     //获取参数，返回参数数组
                   foreach($varArray as $value)
                     echo $value;
                  
                     echo func_get_arg;       //获取单个参数
                   
         }
?>

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