WHY PHP NO WORK

DEAR PROG

WHY NO WORK?
SICP WAS NO HELP.

url_setopt($curl, CURLOPT_POSTFIELDS,"name_f="$_POST["username1"]");
url_setopt($curl, CURLOPT_POSTFIELDS,"name_l="$_POST["username2"]");
url_setopt($curl, CURLOPT_POSTFIELDS,"pass0=$_POST["pass"]");
url_setopt($curl, CURLOPT_POSTFIELDS,"pass1=$_POST["pass"]");
url_setopt($curl, CURLOPT_POSTFIELDS,"email=$_POST["email"]");

To make up for my fail, more performance:

Slower:
if (streln($str) >= 5) // ...
Faster:
if (isset($str[5])) // ...

Slower:
// ... lots of code that may set $var
if (isset($var)) // ...
Faster:
$var = null;
// ... lots of code that may set $var
if ($var !== null) // ...

Surprisingly, equal:
empty($e) === (Bool) $e // the latter gives an error if $e is unset, tho.

Slower:
$e="eval(\"\$e\");";
eval($e);
Faster:
for(;;);

Obvious:
preg_replace("/whut/", "what", $whut) < str_replace("whut", "what", $whut);

Teh sux:
$var = "myprop" . $id;
$class->$var[5]; // Buggy, too.
Teh win:
$class->{"myprop" . $id}[5];

Should work, but doesn't:
{"func" . $i}(); // $this->{"func" . $i}(); works.