preg_replace() not working properly - am i using it right?

[benjy]

ok i need a LOT of help here. what i have is a html form (with a tiny bit of php in it) and a php file that takes the variables in the form and does stuff with them
heres the form:

<form method="post" action="dostuff.php">
name:<br>
<input type="text" name="name"><br>
email:<br>
<input type="text" name="email"><br>
[url]http://[/url]<br>
<input type="text" name="url"><br>
location:<br>
<input type="text" name="country"><br>
<input type="submit" value="submit">
<textarea name="layout" rows="1"><?php include ("indivtxt.txt"); ?></textarea>
</form>

ok as you can see there are 5 variables ($name, $email, $url, $country, $layout) and in a textarea the file "indivtxt.txt" has been included. within the file "indivtxt.txt" there will be 4 things that a user has put their using a different file ([[name]] [[email]] [[url]] [[location]])
heres the php:

<?php

$keyword_name = "[[name]]" ;
$replacement_name = "$name";
preg_replace("/\b$keyword_name\b/i", "$replacement_name", $layout); 

$keyword_email = "[[email]]" ;
$replacement_email = "$email";
preg_replace("/\b$keyword_email\b/i", "$replacement_email", $layout);

$keyword_url = "[[url]]" ;
$replacement_url = "$url";
preg_replace("/\b$keyword_url\b/i", "$replacement_url", $layout);

$keyword_location = "[[location]]" ;
$replacement_location = "$country";
preg_replace("/\b$keyword_location\b/i", "$replacement_location", $layout);



$filename = 'dog.txt';



if (is_writable($filename)) {


if (!$handle = fopen($filename, 'a')) {
     print "Cannot open file ($filename)";
     exit;
}


if (!fwrite($handle, $layout)) {
    print "Cannot write to file ($filename)";
    exit;
}

print "Success";

fclose($handle);

} else {
    print "The file $filename is not writable";
}




?>

now here what i want to do. once a user has submitted the form i want the php to recognise that there is [[name]] [[email]] etc. in the variable $layout and replace them with the variables from the form ($name, $email etc) then write the variable $layout to the file "dog.txt". but, the preg_replace function isnt doing anything and just comes out with a string of text in the files "dog.txt" that says ([[name]] [[email]] [[url]] [[location]]) what have i done wrong?

[Weedpacket]

I think the problem may be that

1. [ and ] have special meaning in regexps and would have to be escaped to be taken literally, and

2. aren't recognised as word characters for by \b

3. You never actually change the value of $layout and just through the altered version away

So;

1. Change [ and ] to [ and ] in the search strings (or use preg_quote()

2. Lose the \b (they're not actually contributing anything useful)

3. use $layout = preg_replace(...)

And consider also the fact that the search and replacement arguments of preg_replace() can be arrays: do the whole lot with one call to the function.