PHP Arrays Turning an Array into a String

PHP Arrays

Turning an Array into a String

Problem

You have an array, and you want to convert it into a nicely formatted string.

Solution

Use join():

            // make a comma delimited list
            $string = join(',' , $array);

Or loop yourself:

            $string = ' ' ;

            foreach ($array as $key => $value) {
                    $string .= ",$value";
            }

            $string = substr($string, 1); // remove leading ","

Discussion

If you can use join(), do; it’s faster than any PHP-based loop. However, join() isn’t very flexible. First, it places a delimiter only between elements, not around them. To wrap elements inside HTML bold tags and separate them with commas, do this:

            $left   = '<b>';
            $right = '</b>';

            $html = $left . join("$right,$left", $html) . $right;


Second, join() doesn’t allow you to discriminate against values. If you want to include a subset of entries, you need to loop yourself:

            $string = ' ' ;

            foreach ($fields as $key => $value) {
                    // don't include password

                    if ('password' != $key) {
                           $string .= ",<b>$value</b>";
                    }
            }

            $string = substr($string, 1); // remove leading ","


Notice that a separator is always added to each value and then stripped off outside the loop. Although it’s somewhat wasteful to add something that will be subtracted later, it’s far cleaner and efficient (in most cases) than attempting to embed logic inside of the loop. To wit:

            $string = ' ' ;
            foreach ($fields as $key => $value) {
                    // don't include password
                    if ('password' != $value) {
                           if (!empty($string)) { $string .= ','; }
                           $string .= "<b>$value</b>";
                    }
            }

Now you have to check $string every time you append a value. That’s worse than the simple substr() call. Also, prepend the delimiter (in this case a comma) instead of appending it because it’s faster to shorten a string from the front than the rear.