如何将函数的参数作为变量返回另一个值？

to be more clear .... :

$var = "value";
function func($var){
    $sql=mysql_query("...$var...");
    $res = mysql_result($sql);
    //$var = $res;
}
echo("$value");

I want from the last line to display $res value, Thanks.

by assigning $var="value" doesn't mean that is what is passed into the function. You have to call the function with any value you want and that value will be put into the $var variable within the func function.

What if you did:

$var = "value";
function func($var){
    $sql=mysql_query("...$var...");
    $res = mysql_result($sql);
    return $res;
}

$ssn = func($var);  
# you could also do func("value");
echo("$ssn");