PHP preg_match_all search and replace

Question

I have tried about a million different regexes and I just can't wrap my head around this one (admittedly a lot of regex is out of my grasp).

In my text I have variables like this:

{{$one}}
{{$three.four.five}}
{{$six.seven}}

And I have an array with all the replaces for them (the index for 'one' is 'one' etc) but some may be missing.

I want to replace from the array if it exists and if not leave the text alone.

What regex can I use to preg_match_all of the variables in $text in the snippet below, replace from $replace where appropriate and echo out to the browser?

<?php
    $replaces = array('testa.testb.testc' => '1', 'testc.testa' => '2', 'testf' => '3');
    $text = '{{$testa.testb.testc}}<br>{{$testc.testa}}<br>{{$testf}}<br>{{$aaaaa}}<br>';

    preg_match_all('/\{\{\$(\w+)\}\}/e', $text, $matches);

    foreach($matches as $match)
    {
        $key = str_replace('{{$', '', $match);
        $key = str_replace('}}', '', $key);

        if(isset($replaces[$key]))
            $text = str_replace($match, $replaces[$key], $text);
    }

    // I want to end up echo'ing:
    //   1<br>2<br>3<br>{{$aaaaa}}<br>

    echo $text;
?>

http://codepad.viper-7.com/4INvEE

This:

'/\{\{\$(\w+)\}\}/e'

like in the snippet, is the closest I have gotten.

It has to work with the does in the variable names too.

Thanks in advance for all the help!

Answer 1

This is a very good case for using preg_replace_callback() but first let's polish your regex:

1. Get rid of the e modifier, it's deprecated and you don't need it since we're going to use preg_replace_callback()

   /\{\{\$(\w+)\}\}/
   

2. We don't need to escape {{}} in this case, PCRE is smart enough to tell that they are not meant as quantifiers

   /{{\$(\w+)}}/
   

3. Since you got dots in your input, we need to change \w otherwise it will never match. [^}] is perfect since it means match anything except }

   /{{\$([^}]+)}}/
   

4. I tend to use different delimiters, this is not required:

   #{{\$([^}]+)}}#
   

Let's get to serious business, the use identifier is going to be of great help here:

$replaces = array('testa.testb.testc' => '1', 'testc.testa' => '2', 'testf' => '3');
$text = '{{$testa.testb.testc}}<br>{{$testc.testa}}<br>{{$testf}}<br>{{$aaaaa}}<br>';

$output = preg_replace_callback('#{{\$([^}]+)}}#', function($m) use ($replaces){
    if(isset($replaces[$m[1]])){ // If it exists in our array
        return $replaces[$m[1]]; // Then replace it from our array
    }else{
        return $m[0]; // Otherwise return the whole match (basically we won't change it)
    }
}, $text);

echo $output;

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Answer 2

Well you are just using $matches and not $matches[0], that's why the code you posted does not work.

And your regex doesn't count the . with the \w, so let'z try with [\w.]+

(I used $matches[1] that contains directly the key we need, and then we don't need to use str_replace 2 times more)

$replaces = array('testa.testb.testc' => '1', 'testc.testa' => '2', 'testf' => '3');
$text = '{{$testa.testb.testc}}<br>{{$testc.testa}}<br>{{$testf}}<br>{{$aaaaa}}<br>';

preg_match_all('/\{\{\$([\w.]+)\}\}/', $text, $matches);

var_dump($matches[1]);

foreach($matches[1] as $match)
{
    if(isset($replaces[$match]))
    {
        $text = str_replace('{{$'.$match.'}}', $replaces[$match], $text);
    }
}

echo $text;

This works and returns :

1
2
3
{{$aaaaa}}