<?php
$username = 'test';
$email = 'test@test.com';
$str = 'This is a test for $username. I am sending mail to some person $email.';
echo $str. "\n";
// This is a test for $username. I am sending mail to some person $email.
eval("\$str = \"$str\";"); echo $str. "\n";
// This is a test for test. I am sending mail to some person test@test.com.
PD9waHAKCiR1c2VybmFtZSA9ICd0ZXN0JzsKJGVtYWlsID0gJ3Rlc3RAdGVzdC5jb20nOwokc3RyID0gJ1RoaXMgaXMgYSB0ZXN0IGZvciAkdXNlcm5hbWUuIEkgYW0gc2VuZGluZyBtYWlsIHRvIHNvbWUgcGVyc29uICRlbWFpbC4nOwoKZWNobyAkc3RyLiAiXG4iOwovLyBUaGlzIGlzIGEgdGVzdCBmb3IgJHVzZXJuYW1lLiBJIGFtIHNlbmRpbmcgbWFpbCB0byBzb21lIHBlcnNvbiAkZW1haWwuCmV2YWwoIlwkc3RyID0gXCIkc3RyXCI7Iik7CmVjaG8gJHN0ci4gIlxuIjsKLy8gVGhpcyBpcyBhIHRlc3QgZm9yIHRlc3QuIEkgYW0gc2VuZGluZyBtYWlsIHRvIHNvbWUgcGVyc29uIHRlc3RAdGVzdC5jb20u