Title capitalisation function. Converts strings to title case.

title_caps.php

<?php
// Title capitalisation function
function title_caps($string) {
  // Needs work on recognising prepositions
  $conjunctions = [ 'an', 'and', 'as', 'at', 'but', 'by', 'else', 'etc', 'for', 'from', 'if', 'in', 'into', 
                    'is', 'nor', 'of', 'off', 'on', 'or', 'per', 'out', 'over', 'so', 'the', 'then', 'to', 
                    'up', 'via', 'vs', 'when', 'with', 'yet' ];

  // Uppercase first letter of all words
  $string = preg_split('/(\W+)/', strtolower($string), -1, PREG_SPLIT_DELIM_CAPTURE);
  foreach ($string as $key => $s) $string[$key] = ucwords($s);
  $string = implode('', $string); // Result: toys-r-us = Toys-R-Us

  // Make all conjunctions and articles lowercase
  foreach ($conjunctions as $word) {
    $pattern = "/(^|\s|[[:punct:]])" . ucwords($word) . "($|\s|[[:punct:]])/";
    for ($i = 0; $i < preg_match_all($pattern, $string); $i++) {
      $string = preg_replace_callback(
                  $pattern,
                  function($matches) { 
                    return strtolower($matches[0]); 
                  },
                  $string
      );
    }
  }

  // Single character words to lowercase
  $pattern = "/(^|\s|[[:punct:]])[A-Z]($|\s|[[:punct:]])/";
  for ($i = 0; $i < preg_match_all($pattern, $string); $i++) {
    $string = preg_replace_callback(
                $pattern,
                function($matches) { 
                  return strtolower($matches[0]); 
                },
                $string
    );
  }

  // Capitalise the first and last word
  $string = explode(' ', ucfirst($string)); // First word
  $string[count($string) - 1] = ucfirst($string[count($string) - 1]); // Last word
  return implode(' ', $string);
}