Creating a function to replace strings that have been gotten from an XML file

Question

I am creating a function that replaces certain parts of a string with predefined constants, for this I have created this function:

<?php

function ReplaceWithPath($string)
{
    $toReplace = ["~~BASEPATH~~" => ABSPATH, "~~LIBPATH~~" => LIBPATH];

    foreach ($toReplace as $replace => $replacement)
    {
        if (preg_match($replace, $string))
            return str_replace($replace, $replacement, $string);
        else
            continue;
    }
    return false;
}

?>

But for some reason, when I use it it does not give me a proper result, but instead boolean false.

I am using the function in my config file as such:

<?php

$cfg_file = str_replace("\\", "/", dirname(__FILE__)) . "/web.config.xml";
$cfg = simplexml_load_file($cfg_file);

define("ABSPATH", $cfg->paths->basepath);

require_once 'library/functions/ReplaceWithString.php';
define("LIBPATH", ReplaceWithPath($cfg->paths->libpath));
var_dump(LIBPATH);

?>

The part of the XML file in question is this:

<paths>
  <basepath>E:/projects/php/site/site/</basepath>
  <libpath>~~BASEPATH~~library/</libpath>
  <classpath>~~LIBPATH~~class/</classpath>
  <traitpath>~~LIBPATH~~trait/</traitpath>
</paths>

I need to be able to change the parts that are ~~BASEPATH~~ with ABSPATH but it just return boolean false.

Edit

After testing, I have found that it is the fact that there are multiple constants in the array ($toReplace) that is causing this not to work. WHY IT DO DIS?!?!?!

New function created:

function ReplacePathPart($path)
{
    $replaced = "";
    $toReplace = array(
        '!!BASEPATH!!'=>ABSPATH, 
        '!!LIBPATH!!'=>LIBPATH
    );

    foreach ($toReplace as $replace => $replacement)
    {
        $replaced = str_replace($replace, $replacement, $path);
    }

    return $replaced;
}

Amended config file:

<?php

$cfg_file = str_replace("\\", "/", dirname(__FILE__)) . "/config/web.config.xml";
$cfg = simplexml_load_file($cfg_file);

define("ABSPATH", $cfg->paths->basepath);
require_once 'library/functions/ReplaceWithString.php';
define("LIBPATH", ReplacePathPart($cfg->paths->libpath));
define("CLASSPATH", ReplacePathPart($cfg->paths->classpath));

print ABSPATH . " |abspath<br />";
print LIBPATH . " |libpath<br />";
print CLASSPATH . " |classpath<br />";

?>

Output:

E:/projects/php/site/site/ |abspath
!!BASEPATH!!library/ |libpath
!!BASEPATH!!library/class/ |classpath

Doesn't this just work: $replacedResult = str_replace(array_keys($toReplace), array_values($toReplace), $string); ? — Rizier123
– Rizier123, Commented Dec 7, 2015 at 16:15
BTW: In ~~BASEPATH~~, ~ will be seen as delimiter for your preg_match() call and your regex will fail with unescaped delimiters — Rizier123
– Rizier123, Commented Dec 7, 2015 at 16:17
You don't need a loop, str_replace() also can take arrays as argument, as I said just use: $replacedResult = str_replace(array_keys($toReplace), array_values($toReplace), $string); you overthink this way too much.; Now you use $path each source which doesn't change and save it in $replaced, that's why only the last one gets replaced — Rizier123
– Rizier123, Commented Dec 7, 2015 at 16:40
@Rizier123, I got the wrong end of the stick on that one! My bad and can you add as an answer? — anon
– anon, Commented Dec 7, 2015 at 16:41

Rizier123 · Accepted Answer · 2015-12-07 17:03:09Z

It seems like you are overthinking this way too much. Drinking a cup of coffee(☕) or reading this answer should solve the problem:

First off your original function:

function ReplaceWithPath($string)
{
    $toReplace = ["~~BASEPATH~~" => ABSPATH, "~~LIBPATH~~" => LIBPATH];

    foreach ($toReplace as $replace => $replacement)
    {
        if (preg_match($replace, $string))
            return str_replace($replace, $replacement, $string);
        else
            continue;
    }
    return false;
}

In your preg_match() call ~ will be seen as delimiter for the regex string. So in your strings: ~~BASEPATH~~, ~~LIBPATH~~ you then have unescaped delimiters, which means your regex will fail.

The return statement in your foreach loop would immediately stop the function call and would only replace 1 search => replace element.

Searching for the search strings and looping through the replacement array is unnecessary. Since with str_replace() you already search for the search strings + you can pass arrays to the function:

mixed str_replace ( mixed $search , mixed $replace , mixed $subject [, int &$count ] )

Now in your second try you get a bit closer to the solution, but still make some logical mistakes:

function ReplacePathPart($path)
{
    $replaced = "";
    $toReplace = array(
        '!!BASEPATH!!'=>ABSPATH, 
        '!!LIBPATH!!'=>LIBPATH
    );

    foreach ($toReplace as $replace => $replacement)
    {
        $replaced = str_replace($replace, $replacement, $path);
    }

    return $replaced;
}

You still loop through the replacement array and now you use $path as source which will never change and in each iteration you overwrite $replaced with the replaced string. So at the end you end up with only replacing the last search => replace element.

The solution to your problem is simple:

function ReplacePathPart($path)
{
    $toReplace = array(
        '!!BASEPATH!!'=>ABSPATH, 
        '!!LIBPATH!!'=>LIBPATH
    );    

    return str_replace(array_keys($toReplace), array_values($toReplace), $path);

}

As I said str_replace() can take arrays as arguments, so with array_keys($toReplace) you search for your keys(!!BASEPATH!!, !!LIBPATH!!) and replace them with the values(ABSPATH, LIBPATH), which you get with array_values($toReplace).

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