Run a variable through several functions

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.

This one is probably the most readable way. You can nest the function calls, but it won't increase readability. — Felix Kling, Jan 12 '13 at 14:27
@Felix I agree that nesting decreases readability. really no other way? — mauris, Jan 12 '13 at 14:29
you could nest function calls, however php is not javascript or ruby , you would need a custom class wrapping strings for "sequential calls". — mpm, Jan 12 '13 at 14:30
Your current code is just fine, with PHP you can't do better. — Gras Double, Jan 12 '13 at 14:34

score 3 · Accepted Answer · answered Jan 12 '13 at 14:35

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.

+1 I was thinking about `call_user_func` as well. It's not necessarily pretty, but an interesting approach. — Felix Kling, Jan 12 '13 at 15:08

score 0 · Answer 2 · answered Jan 12 '13 at 14:29

use this as a combination of all five

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

but use as you are trying.because it is good practice rather than writing in one line.

Run a variable through several functions

2 Answers2