PHP str_replace with function

Question

Is it possible use str_replace() and use function in replace?

$value = \"gal($data)\";

$replace = str_replace($dat, $value, $string);


        

Answer 1

PHP has a function called preg_replace_callback that does this. When you pass it a callback function, it will pass each match through your function. You can choose to replace, based upon the matched value, or ignore it.

As an example, suppose I have a pattern that matches various strings, such as [a-z]+. I may not want to replace every instance with the same value, so I can call a function upon eat match found, and determine how I ought to respond:

function callback ($match) {
    if ($match[0] === "Jonathan")
        return "Superman";
    return $match[0];
}

$subject = "This is about Jonathan.";
$pattern = "/[a-z]+/i";
$results = preg_replace_callback($pattern, "callback", $subject);

// This is about Superman.
echo $results;

Note in our callback function how I am able to return special values for certain matches, and not all matches.

Expanding Abbreviations

Another example would be a lookup. Suppose we wanted to find abbreviations of programming languages, and replace them with their full titles. We may have an array that has abbreviations as keys, with long-names as values. We could then use our callback ability to lookup the full-length names:

function lookup ($match) {
    $langs = Array(
        "JS"  => "JavaScript", 
        "CSS" => "Cascading Style Sheets", 
        "JSP" => "Java Server Pages"
    );
    return $langs[$match[0]] ?: $match[0];
}

$subject = "Does anybody know JS? Or CSS maybe? What about PHP?";
$pattern = "/(js|css|jsp)/i";
$results = preg_replace_callback($pattern, "lookup", $subject);

// Does anybody know JavaScript? Or Cascading Style Sheets maybe? What about PHP?
echo $results;

So every time our regular expression finds a match, it passes the match through lookup, and we can return the appropriate value, or the original value.