Expanding variables within a string?

Is it possible to expand variables within a string? For example:

$var = grape;
$str1 = 'The item is a $var';

Now do some operation on $str1, so that the output turns out to be:

The item is a grape

I am not talking about putting double quotes around the string when it is set or doing some sort of search/replace on a specific variable name. I would like to know if there is a way to get ALL the variables within a string to evaluate after the string is already set.

~Lauxa

 

    $str='The item is a $var';
    $var="grape";
    eval("\$str=\"$str\";");
    echo $str;

Code (markup):

 

Awesome, thanks a ton!

 

also this will work and easier to do

$var="grape";

$str="The item is a ".$var;

 

This will not work. Lauxa asked for a solution where you first assign $str and then $var, not $var first and then $str.

 

Examples: http://php.net/eval