Perl to PHP conversion

[zishan]

Hello,
I need help in converting following perl script functions into php, can anyone pls?

sub Encrypt {
my ($source,$key,$pub_key) = @_;
my ($cr,$index,$char,$key_char,$enc_string,$encode,$f irst,
$second,$let1,$let2,$encrypted,$escapes) = '';
$source = &rot13($source);
$cr = '·¨*';
$source =~ s/[\n\f]//g;
$source =~ s/[\r]/$cr/g;
while ( length($key) < length($source) ) { $key .= $key }
$key=substr($key,0,length($source));
while ($index < length($source)) {
$char = substr($source,$index,1);
$key_char = substr($key,$index,1);
$enc_string .= chr(ord($char) ^ ord($key_char));
$index++;
}
for (0..255) { $escapes{chr($_)} = sprintf("%2x", $_); }
$index=0;
while ($index < length($enc_string)) {
$char = substr($enc_string,$index,1);
$encode = $escapes{$char};
$first = substr($encode,0,1);
$second = substr($encode,1,1);
$let1=substr($pub_key, hex($first),1);
$let2=substr($pub_key, hex($second),1);
$encrypted .= "$let1$let2";
$index++;
}
return $encrypted;
}
sub rot13{
my $source = shift (@_);
$source =~ tr /[a-m][n-z]/[n-z][a-m]/;
$source =~ tr /[A-M][N-Z]/[N-Z][A-M]/;
$source = reverse($source);
return $source;
}

[Motoma]

Perhaps you could tell us what this method of encryption is called? Or explain the way the technique works?
It would be easier to rewrite the method than convert code line by line.