我如何制作只在通过URL发送某个变量id时才运行的IF语句？

Is it possible to make an IF clause in php that will only trigger if i have encoded a specific variable in the url?

I have a php page which will get and output query results without page refresh. When a user clicks on a specific query result, that value is sent via url to the same page which then reruns this script with that query result as the new search parameter.

Only thing is, first time the page is run i need to find a way to bypass the echo statements and the attempts to $_GET data from the url, because there is none.

so essentially some kind of if clause that could be like

IF(url variable value = 'id')
{
$variabledata=$_GET['var1'];
echo $variabledata;
}

ELSE nothing

You can do it like this:

if (isset($_GET['var1'])) {
   $variabledata=$_GET['var1'];
   echo $variabledata;
}

so the content of the if block will only be executed if the parameter var1 was sent.

$_REQUEST works for GET and POST

if($_REQUEST['url_variable_value'] == 'id'){
    $variabledata=$_GET['var1'];
    echo $variabledata;
} else {
    // nothing
}


// http://example.com/somewhere/?url_variable_value=id&var1=the_data
// output: "the_data"

you can check this when you get the url

if (isset($_GET['var1']) &&  $variabledata=$_GET['var1']) {
     echo $variabledata;
}