Sort an array of sentences alphabetically, ignoring the first word if it equals 'the' (case insensitive)

Question

function order_ignore_the($a, $b){
     // orders sentences ascending alphabetically, ignoring the  work "the"
     $args = func_get_args();
     foreach($args as $k=>$v){
          
          $sort = explode(" ",$v);
          $args[$k] = (strtolower($sort[0]) == "the" ? $sort[1] : $sort[0]);
     }
     
    return strcmp($args[0], $args[1]);
}

usort($array_of_sentences,'order_ignore_the');

Answer 1

I'm not sure what you're doing there, but I think it can get shortened to this.

function order_ignore_the($a, $b) {
    return strcmp(
        strcasecmp(substr($a, 0, 3), "the") != 0 ? $a : substr($a, 3),
        strcasecmp(substr($b, 0, 3), "the") != 0 ? $b : substr($b, 3)
    );
}

Be warned that this is not tested.

Edit: Long version with explanation:

function order_ignore_the($a, $b) {
    // Variables for later use
    $checkedA = $a;
    $checkedB = $b;

    // Compare the first three letters case-insensitive against "the"
    if(strcasecmp(substr($checkedA, 0, 3), "the") == 0) {
        // strip the "the" from the string
        $checkedA = substr($checkedA, 3);
    }
    // Repeate for $b
    if(strcasecmp(substr($checkedB, 0, 3), "the") == 0) {
        $checkedB = substr($checkedB, 3);
    }

    // Compare both strings
    return strcmp($checkedA, $checkedB);
}

Yes, it's swapped, I'm checking in the short version if the string does not match "the", and here I'm checking if it does match.

Answer 2

With some testing, it should look like the below

function order_ignore_the($a, $b) {
    return strcasecmp(
        strcasecmp(substr($a, 0, 4), "the ") != 0 ? $a : substr($a, 4),
        strcasecmp(substr($b, 0, 4), "the ") != 0 ? $b : substr($b, 4)
    );
}

Main differences being:

• Widening the search for "the" to include the space after. Otherwise, you're matching on things like "theater", etc.
• The last substr should likewise have start position 4. Otherwise, you're comparing on the space after "the".
• You'll want the main comparison to ignore capitalization, too.

Answer 3

I took a moment to compile a list of real movie titles which represent some squirrelly fringe cases.

I arrived at a one-liner that relies on regex for best accuracy that doesn't fail when the leading The word is not immediately followed by a space. Notice that one real movie title below starts with the word "the", but the fourth character is not a space, so your exploding technique will not accurately remove it.

Your custom function explodes on spaces and assumes that all titles will contain at least one space -- this is a falsehood. Your code will generate Warning: Undefined array key 1 errors every time it encounters a movie without a space.

Another problem with your use of explode() is that you are not limiting the generated output to 2 elements. This will lead to incorrect results when comparing The Matrix, The Matrix 2, and The Matrix 3. Effectively, the The words will be stored as [0], then the word Matrix as [1], and any/all subsequent characters in the title are doomed to go unused.

Note, because you are using func_get_args() in your custom function and you never reference $a or $b, you don't actually need to declare them as arguments for your script to run.

Effectively, the preg_replace() call trims off the qualifying The in the temporary array which is only used for sorting the original array.

While regex is generally a more expensive technique than non-regex techniques, it never revisits any values because it is not called within the sorting iterations.

This snippet will deliver a much more accurate sort than the code you have posted.

Code: (Demo)

$array = [
   'The Theory of Everything',
   'The Mummy Returns',
   'The Mummy',
   'Then Came You',
   'The One',
   'The',
   'The 100',
   'The Matrix',
   'Theft',
   'The...',
   '300',
   'The 300 Spartans',
   'Mad Max',
   'Then',
   'The Martian',
];

array_multisort(preg_replace('/^the\b ?/i', '', $array), $array);
var_export($array);

Output:

array (
  0 => 'The',
  1 => 'The...',
  2 => 'The 100',
  3 => '300',
  4 => 'The 300 Spartans',
  5 => 'Mad Max',
  6 => 'The Martian',
  7 => 'The Matrix',
  8 => 'The Mummy',
  9 => 'The Mummy Returns',
  10 => 'The One',
  11 => 'Theft',
  12 => 'Then',
  13 => 'Then Came You',
  14 => 'The Theory of Everything',
)