PHP Sort by Scripture (Bible)

<?php

function _scripturebooks() {
  return array("Genesis", "Exodus", "Leviticus", "Numbers", "Deuteronomy", "Joshua", "Judges", "Ruth", "1 Samuel", "2 Samuel", "1 Kings", "2 Kings", "1 Chronicles", "2 Chronicles", "Ezra", "Nehemiah", "Esther", "Job", "Psalm", "Proverbs", "Ecclesiastes", "Song of Solomon", "Isaiah", "Jeremiah", "Lamentations", "Ezekiel", "Daniel", "Hosea", "Joel", "Amos", "Obadiah", "Jonah", "Micah", "Nahum", "Habakkuk", "Zephaniah", "Haggai", "Zechariah", "Malachi", "Matthew", "Mark", "Luke", "John", "Acts", "Romans", "1 Corinthians", "2 Corinthians", "Galatians", "Ephesians", "Philippians", "Colossians", "1 Thessalonians", "2 Thessalonians", "1 Timothy", "2 Timothy", "Titus", "Philemon", "Hebrews", "James", "1 Peter", "2 Peter", "1 John", "2 John", "3 John", "Jude", "Revelation");
}

 function scripturesort($a, $b) {
      if ($a == $b) {return 0;}
	    $order=_scripturebooks();

	    $fa = $a;
	    $fb = $b;
	    
	    if (preg_match('/^..(.+?)\b/', $a, $matches))
	      $a = trim(substr($matches[0],0,4));
	    else
	      $a = '';

	    if (preg_match('/^..(.+?)\b/', $b, $matches))
	      $b = trim(substr($matches[0],0,4));
	    else
	      $b = '';

	    similar_text($a, $b, $p);
	    if($p > 75) {
	    	preg_match('/(.+?)([\d]+)/', $fa, $matches);
	    	$na = intval(@$matches[2]);
	    	preg_match('/(.+?)([\d]+)/', $fb, $matches);
	    	$nb = intval(@$matches[2]);
	    	if($na == $nb) {
		    	preg_match('/(.+?)([\d]+).*?:([\d]+)/', $fa, $matches);
		    	$n2a = intval(@$matches[3]);
		    	preg_match('/(.+?)([\d]+).*?:([\d]+)/', $fb, $matches);
		    	$n2b = intval(@$matches[3]);
		    	return ($n2a < $n2b) ? -1 : 1;
	    	} else
	    	return ($na < $nb) ? -1 : 1;
	    }

	    $position = empty($a) ? NULL : key(preg_grep('/^'.$a.'(.*)\b/', $order));
	    $position2 = empty($b) ? NULL : key(preg_grep('/^'.$b.'(.*)\b/', $order));

	    if ($position2!==NULL && $position!==NULL) {return ($position < $position2) ? -1 : 1;}
	    if($position!==NULL) {return -1;}
	    if($position2!==NULL) {return 1;}

	    return ($a < $b) ? -1 : 1;
	}

  $scriptures = array(
    'Genesis',
    'Genesis 1:12',
    'Genesis 1:1',
    'Revelation',
    'Leviticus 2:10',
    'Exodus 3:4',
    'Nonexistent',
    'Job',
    '',
    'Matthew',
  );
  usort($scriptures, 'scripturesort');
  var_dump($scriptures);


/**
 * Reduce a scripture reference into something that an SQL ORDER BY
 * clause should correctly order as either a numeric or non-numeric.
 *
 * Derived from https://gist.github.com/Xeoncross/9534124.
 *
 * Returns a string with no whitespace.
 */
function scripture2db_orderable($a) {
  $order=_scripturebooks();

  $fa = $a;
  if (preg_match('/^..(.+?)\b/', $a, $matches))
    $a = trim(substr($matches[0],0,4));
  else
    $a = '';

  preg_match('/(.+?)([\d]+)/', $fa, $matches);
  $na = intval(@$matches[2]);

  preg_match('/(.+?)([\d]+).*?:([\d]+)/', $fa, $matches);
  $n2a = intval(@$matches[3]);

  $position = empty($a) ? NULL : key(preg_grep('/^'.$a.'(.*)\b/', $order));
  if ($position === NULL)
    $position = 999-1;

  return sprintf('%03d.%03d:%03d', $position+1, $na, $n2a);
}

$scriptures_orderable = array();
foreach ($scriptures as $scripture)
{
  $key = scripture2db_orderable($scripture);
  $scriptures_orderable += array($key => array());
  $scriptures_orderable[$key][] = $scripture;
}
ksort($scriptures_orderable);
var_dump($scriptures_orderable);

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