Adding conditional formatting and punctuation to a set of variables

Question

I often need to list items separated by comma, space or punctuation, addresses are a classic example (This is overkill for an address and is for the sake of an example!):

echo "L$level, $unit/$num $street, $suburb, $state $postcode, $country.";
//ouput: L2, 1/123 Cool St, Funky Town, ABC 2000, Australia.

As simple as it sounds, is there an easy way to "conditionally" add the custom separators between variables only if the variable exists? Is it necessary to check if each variable is set? So using the above, another address with less detail may output something like:

//L, / Cool St, , ABC , .

A slightly arduous way of checking would be to see if each variable is set and display the punctuation.

if($level){ echo "L$level, "; }
if($unit){ echo "$unit"; }
if($unit && $street){ echo "/"; }
if($street){ echo "$street, "; }
if($suburb){ echo "$suburb, "; }
//etc...

It would be good to have a function that could automatically do all the stripping/formatting etc:

somefunction("$unit/$num $street, $suburb, $state $postcode, $country.");

---

Another example is a simple csv list. I want to output x items separated by comma:

for($i=0; $i=<5; $i++;){ echo "$i,"; }
//output: 1,2,3,4,5,

In a loop for example, what's the best way of determining the last item of an array or the loop condition is met to not include a comma at the end of the list? One long way around this I've read of is to put a comma before an item, except the first entry something like:

$firstItem = true; //first item shouldn't have comma
for($i=0; $i=<5; $i++;){
  if(!$firstItem){ echo ","; }
  echo "$i";
  $firstItem = false;
}

Answer 1

I always find that its both faster and easier to use the language's array methods. For instance, in PHP:

<?php
echo join(',', array('L'.$level, $unit.'/'.$num, 
          $street, $suburb, $state, $postcode, $country));

Answer 2

While Phillip's answer addresses your question, I wanted to supplement it with the following blog post by Eric Lippert. Although his discussion is in c#, it applies to any programming language.

Answer 3

There's a simple solution to your second problem:

for($i=0; $i<=5; $i++)
    $o .= "$i,";
echo chop($o, ',');

Answer 4

Philip's solution is probably best when working with arrays (if you don't have to filter out empty values), but if you can't use the array functions--for instance, when dealing with query results returned from mysqli_fetch_object()--then one solution is just a simple if statement:

$list = '';
$row=mysqli_fetch_object($result);
do {
    $list .= (empty($list) ? $row->col : ", {$row->col}");
} while ($row=mysqli_fetch_object($result));

Or, alternatively:

do {
    if (isset($list)) {
     $list .= ", {$row->col}";
    } else $list = $row->col;
} while ($row=mysqli_fetch_object($result));

To build a list and filter out empty values, I would write a custom function:

function makeList() {
    $args = array_filter(func_get_args()); // as per Jon Benedicto's answer
    foreach ($args as $item) {
        if (isset($list)) {
            $list .= ", $item";
        } else {
            $list = $item;
        }
    }
    if (isset($list)) {
        return $list;
    } else return '';
}

Then you can call it like so:

$unitnum = implode('/',array_filter(array($unit,$num)));
if ($unitnum || $street) {
    $streetaddress = trim("$unitnum $street");
} else $streetaddress = '';
if ($level) {
    $level = "L$level";
}
echo makeList($level, $streetaddress, $suburb, $state $postcode, $country).'.';

Answer 5

For your first example, you can use arrays in conjunction with a few of the array methods to get the desired result. For example:

echo join(', ', array_filter(array("L$level", join(' ', array_filter(array(join('/', array_filter(array($unit, $num))), $street))), $suburb, join(' ', array_filter(array($state, $postcode))), $country))) . '.';

This one-liner is quite complicated to read, so one can always wrap the array, array_filter and join calls into a separate method, and use that:

function merge($delimiter)
{
    $args = func_get_args();
    array_shift($args);
    return join($delimiter, array_filter($args));
}

echo merge(', ', "L$level", merge(' ', merge('/', $unit, $num), $street), $suburb, merge(' ', $state, $postcode), $country) . '.';

You need the array_filter calls to remove the empty entries, otherwise the delimeters would still be printed out.

For your second example, add the items to an array, then use join to insert the delimeter:

$arr = array();
for($i=0; $i=<5; $i++)
{
    $arr[] = $i;
}
echo(join(',', $arr));

Answer 6

<?php
    $level  = 'foo';
    $street = 'bar';
    $num    = 'num';
    $unit   = '';

    // #1: unreadable and unelegant, with arrays
    $values   = array();
    $values[] = $level ? 'L' . $level : null;
    // not very readable ...
    $values[] = $unit && $num ? $unit . '/' . $num : ($unit ? $unit : ($num ? $num : null));
    $values[] = $street ? $street : null;

    echo join(',',  $values);


    // #2: or, even more unreadable and unelegant, with string concenation
    echo trim( 
        ($level ? 'L' . $level . ', ' : '') . 
        ($unit && $num ? $unit . '/' . $num . ', ' : ($unit ? $unit . ', ' : ($num ? $num . ', ': '')) .
        ($street ? $street . ', ': '')), ' ,');

    // #3: hey, i didn't even know that worked (roughly the same as #1):
    echo join(', ', array(
        $level ? 'L' . $level : null,
        $unit && $num ? $unit . '/' . $num : ($unit ? $unit : ($num ? $num : null)),
        $street ? $street : null
    ));
?>

Answer 7

Just take out the last comma, i.e replace it with nothing.

$string1 = "L$level, $unit/$num $street, $suburb, $state $postcode, $country.";
$string1 = eregi_replace(", \.$", "\.", $string1);
echo $string1;

This will do the work.

Answer 8

ok, take that! (but not too serious ^^)

<?php

function bothOrSingle($left, $infix, $right) {
    return $left && $right ? $left . $infix . $right : ($left ? $left : ($right ? $right : null));
}

function leftOrNull($left, $postfix) {
    return $left ? $left . $postfix : null;
}

function rightOrNull($prefix, $right) {
    return $right ? $prefix . $right : null; 
}

function joinargs() {
    $args = func_get_args();
    foreach ($args as $key => $arg) 
        if (!trim($arg)) 
            unset($args[$key]);

    $sep = array_shift($args);
    return join($sep, $args);
}

$level    = 2;
$unit     = 1;
$num      = 123;
$street   = 'Cool St';
$suburb   = 'Funky Town';
$state    = 'ABC';
$postcode = 2000;
$country  = 'Australia';

echo "\n" . '"' . joinargs(', ', rightOrNull('L', $level), bothOrSingle(bothOrSingle($unit, '/', $num), ' ', $street), bothOrSingle($state, ' ', $postcode), bothOrSingle($country, '', '.')) . '"';

// -> "L2, 1/123 Cool St, ABC 2000, Australia."

$level    = '';
$unit     = '';
$num      = '';
$street   = 'Cool St';
$suburb   = '';
$state    = 'ABC';
$postcode = '';
$country  = '';

echo "\n" . '"' . joinargs(
    ', ', 
    leftOrNull(
        joinargs(', ', 
            rightOrNull('L', $level), 
            bothOrSingle(bothOrSingle($unit, '/', $num), ' ', $street), 
            bothOrSingle($state, ' ', $postcode), 
            $country
        ),
        '.'
    )
) . '"';

// -> "Cool St, ABC."


$level    = '';
$unit     = '';
$num      = '';
$street   = '';
$suburb   = '';
$state    = '';
$postcode = '';
$country  = '';

echo "\n" . '"' . joinargs(
    ', ', 
    leftOrNull(
        joinargs(', ', 
            rightOrNull('L', $level), 
            bothOrSingle(bothOrSingle($unit, '/', $num), ' ', $street), 
            bothOrSingle($state, ' ', $postcode), 
            $country
        ),
        '.'
    )
) . '"';

// -> "" (even without the dot!)

?>

yes, i know - looks a bit like brainfuck.