Do you know how to create optional parameters in PHP?

In the previous article " Quickly Generate QR Codes with PHP" I introduced to you how to quickly generate QR codes through PHP. Interested friends can learn about it~

The topic of this article is "How to create optional parameters in PHP"?

Some people may ask what are "optional parameters"?

Optional parameters refers to parameters that will not prevent the function from working even if nothing is passed. In layman's terms, it means that those with default values ​​are optional parameters.

Then if there are completely optional parameters, the program will take their values, but if a parameter is not assigned a value, the program will not stop; usually by providing the function with a default value for the parameter these parameters. But if the function is given a value for an argument during the call, the given argument overrides the default argument and the program will continue to run normally, however if the call does not provide any value to the function, the program will continue to run normally using the default value.

→Note: In order to add more functions to the function when creating a PHP function, we can add parameters, which are similar to variables; the parameters are specified in parentheses after the function name.

Let me introduce you to how to create optional parameters in PHP through two examples:

Example 1:

<?php
function travel($place = "北京")
{
  return "我要去$place.\n";
}
echo travel();
echo travel("上海");
echo travel("深圳");
?>

Output:

我要去北京!
我要去上海!
我要去深圳!

Example 2:

<?php
function timer($hour=00, $min=00, $sec=00)
{
    $time="$hour : $min : $sec.";
    return "定时器设置为： $time <br>";
}
echo timer();
echo timer(10, 30, 0);
echo timer(00, 20, 40);

Output:

定时器设置为： 0 : 0 : 0.
定时器设置为： 10 : 30 : 0.
定时器设置为： 0 : 20 : 40.

Note: When using default parameters, any default parameters must be placed to the right of any non-default parameters; otherwise, the function will not behave as expected Work.

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