变量请求时的默认值

I have one form as below in test1.php

<form action="test.php?CID=25" name="form1" METHOD="POST">
    <input type=text name="YID" VALUE="22" />
    <INPUT TYPE=SUBMIT NAME="SUBMIT" />
</form>

test.php file will request the variable CID and YID.

in classic asp I can request both variable like below.

CID=REQUEST("CID")
YID=REQUEST("YID")

REQUEST will work for both. As CID is a variable which will appear in the hyperlink as below

http://localhost/test.php?CID=25

on submitting the form in test1.php.

in classic asp if any variable is not defined then I can handle the variable as below.

CID=REQUEST("CID"):if isnull(CID) or trim(CID)="" then CID=0
YID=REQUEST("YID"):if isnull(YID) or trim(YID)="" then YID=0

How could it be done in PHP.

For this URL:

http://localhost/test.php?CID=25

If you want the value of CID you would use:

$_GET['CID']

From a POSTed form containing:

<input type=text name="YID" VALUE="22" />

You would use

$_POST['YID']

If you need to test if a veriable is set you can use

$value = isset($_POST['YID']) ? $_POST['YID'] : '';

This is shorthand for

if(isset($_POST['YID'])){
  $value = $_POST['YID'];
} else {
  $value = 0; // or FALSE or null or '' or any default value you want
}

you can do like this

$_REQUEST['CID']==null ? ($CID=0) : ($CID=$_REQUEST['CID']);

or this can be used-

function getIfSet(&$value, $default = 0)
{
    return isset($value) ? $value : $default;
}

$CID = getIfSet($_REQUEST["CID"]);

  $CID = (isset($_GET['CID']) and $_GET['CID'] != '') ? $_GET['CID'] : 0;
  $YID = (isset($_POST['YID']) and $_POST['YID'] != '') ? $_POST['YID'] : 0;