Need some help in porting a code from javascript to PHP

Hello!

Please help me!
I am currently working on a small project. I have port a javascript code to PHP. Don't ask, I just have to. :)
The problem is that I can't get my PHP code work. There are some errors.
The code is an encrypting code.

********************************************************************************
The shortened html:
<form name="fa">
<textarea id="f2"></textarea>
select name="et" onchange="encN=this.selectedIndex+1">
<option selected>1
<option>2
<option>3
<option>4
<option>5
</select>
<input type="button" value="Encode" onclick="writeOut()">

********************************************************************************
The original JavaScript:
<script language="javascript">
var encN=1;
function encodeTxt(s){
s=escape(s);
var ta=new Array();
for(i=0;i<s.length;i++)ta[i]=s.charCodeAt(i)+encN;
return ""+escape(eval("String.fromCharCode("+ta+")"))+encN;
}
function writeOut(){
document.forms["fa"].output.value="<"+"script language=javascript"+">document.write(unescape('%3C%73...bla..bla..bla..%74%3E'));dF('"+encodeTxt(document.forms['fa'].f2.value)+"')<"+"/script>";
}
</script>

NOTE: I have to get this **encodeTxt(document.forms['fa'].f2.value)** part with PHP!


My PHP code is not working! I think I've done my best, I am really just a beginner. Please help!

The error msg is:
Notice: Undefined offset: 67 in \\.host\Shared Folders\htdocs\encoder\encoder.php on line 29

Parse error: syntax error, unexpected T_CONSTANT_ENCAPSED_STRING in \\.host\Shared Folders\htdocs\encoder\encoder.php(32) : eval()'d code on line 1
2          ( I don't know what is this number 2.. Maybe the final string?)

Please help me to fix my code!
Maybe just a few fix, but I can't do more!

Thank you! You are my only hope!

If it's help, the original result of the Javascript (that I want) for "ssp_1-10_img (000).jpg" (without quotes) in the **encodeTxt(document.forms['fa'].f2.value)** part (that I need) is:
ttq%602.21%60jnh%2631%2639111%263%3A/kqh1

********************************************************************************
My PHP code (extracted to a snippet for readability and line numbering by mplungjan, ee zape):

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<?php //first line -- lines here are not edited, because of the line counting.
 
$encN = 1;
 
$txt = "ssp_1-10_img (000).jpg";
$codeKey = 1; // options are: 0 | 1 | 2 | 3 | 4
$encN = $codeKey+1;
 
function escape($str) {
	$str = bin2hex($str);
	$r="";
	for( $a=0; $a<strlen($str); $a+=2 )
	{	
		$r.="%".$str{$a}.$str{$a+1};
	}
	$r = strtoupper($r);
	return $r;
}
 
function encodeTxt($s){
	global $encN;
	$r="";
	$s = escape($s);
	$ta = array();
	for ($i=1; $i<=strlen($s); $i++) {
		$ta{$i} = ord(substr($s, $i, 1))+$encN;
	}
	for ($j=1; $j<=$i; $j++) {
		$r.= chr($ta{$j});
	}
	
	$r = escape(eval($r)).$encN;
	return $r;
}
 
echo encodeTxt($txt);
 ?>