我可以为另一个var分配一个值，我不知道是否存在于一行中？

I'm looking for a better and easy way to do this. I remember I saw a shorthand somewhere.

if (isset($user['passport'])) $passport=$user['passport'];

Edited to let you know what I mean

Classic ASP:

user=request.form("user")
response.write user

ASP doesn't care if user exists, so prints nothing

The same in PHP

$user=$_POST['user'];
echo $user;

PHP prints Notice: Undefined variable

If you need shorthand condition than you can use ternary operator as:

$passport = (isset($user['passport']) ? $user['passport'] : '');

$passport=$user['passport']?$user['passport']:"Value if not set";

Try this :

$passport = ($user['passport'])?: '';

You can use PHP ternary operator for this purpose

Link to learn about ternary operator http://php.net/manual/en/language.operators.comparison.php

Sample php code

<?php
// Example usage for: Ternary Operator
$passport = (isset($user['passport'])) ? $user['passport'] : '';

// The above is identical to this if/else statement
if (isset($user['passport'])) {
    $passport = $user['passport'];
} else {
    $passport = '';
}
?>

Classic ASP 'may not care', but don't be fooled by apparently none existent values. Sometimes they do contain something, e.g. Nothing. This all depends, of course, on the original source of the value.

A quick and dirty method that I tend to use to force variants of a particular type is to append an empty string to the beginning, e.g.:

user = "" & Request.Form("user")
'As a numeric example from a different source...
count = CInt("0" & rs("record_count"))

For PHP you could consider:

$passport = "" . $user[passport];

(I don't know a great deal about PHP, unfortunately.)