Question

I am attempting to run a variable through several functions to obtain a desired outcome.

For example, the function to slugify a text works like this:

        // replace non letter or digits by -
        $text = preg_replace('~[^\\pL\d]+~u', '-', $text);

        // trim
        $text = trim($text, '-');

        // transliterate
        $text = iconv('utf-8', 'us-ascii//TRANSLIT', $text);

        // lowercase
        $text = strtolower($text);

        // remove unwanted characters
        $text = preg_replace('~[^-\w]+~', '', $text);

However, we can see that there is a pattern in this example. The $text variable is passed through 5 function calls like this: preg_replace(..., $text) -> trim($text, ...) -> iconv(..., $text) -> strtolower($text) -> preg_replace(..., $text).

Is there a better way we can write the code to allow a variable sieve through several functions?

One way is to write the above code like this:

$text = preg_replace('~[^-\w]+~', '', strtolower(iconv('utf-8', 'us-ascii//TRANSLIT', trim(preg_replace('~[^\\pL\d]+~u', '-', $text), '-'))));

… but this way of writing is a joke and mockery. It hinders code readability.

Answer 1

Since your “function pipeline” is fixed then this is the best (and not coincidentally simplest) way.

If the pipeline were to be dynamically constructed then you could do something like:

// construct the pipeline
$valuePlaceholder = new stdClass;
$pipeline = array(
    // each stage of the pipeline is described by an array
    // where the first element is a callable and the second an array
    // of arguments to pass to that callable
    array('preg_replace', array('~[^\\pL\d]+~u', '-', $valuePlaceholder)),
    array('trim', array($valuePlaceholder, '-')),
    array('iconv', array('utf-8', 'us-ascii//TRANSLIT', $valuePlaceholder)),
    // etc etc
);

// process it
$value = $text;
foreach ($pipeline as $stage) {
    list($callable, $parameters) = $stage;
    foreach ($parameters as &$parameter) {
        if ($parameter === $valuePlaceholder) {
            $parameter = $value;
        }
    }
    $value = call_user_func_array($callable, $parameters);
}

// final result
echo $value;

See it in action.