Curl quotes (transform straight quotes into curly ones) (PHP5)

curl_quotes.php

<?php

function curl_quotes($str) {
	// Adapted from: https://github.com/kellym/smartquotes.js/blob/master/lib/replacements.js

	// Single quotes
	$sx = "'"; // straight (\u0027)
	$s1 = "‘"; // Opening (\u2018)
	$s2 = "’"; // Closing (\u2019)

	// Double quotes
	$dx = '"'; // straight (\u0022)
	$d1 = "“"; // Opening (\u201C)
	$d2 = "”"; // Closing (\u201D)

	// Primes
	$prime1 = '′'; // Single prime, also for ft (\u2032)
	$prime2 = '″'; // Double prime (\u2033)
	$prime3 = '‴'; // Triple prime (\u2034)
	$prime4 = '⁗'; // Quadruple prime (\u2057)

	// word character range
	$wcr = 'a-zA-ZáàâäãåçéèêëíìîïñóòôöõúùûüýÿæœÁÀÂÄÃÅÇÉÈÊËÍÌÎÏÑÓÒÔÖÕÚÙÛÜÝŸÆŒ';
	// word groups
	$word = "[${wcr}_0-9]";
	$nonword = "[^${wcr}_0-9]";

	// quadruple prime
	$str = preg_replace(
		"/${sx}${sx}${sx}${sx}/i",
		"${prime4}",
		$str
	);

	// triple prime
	// [/'''/g, retainLength => '\u2034' + (retainLength ? '\u2063\u2063' : '')],
	$str = preg_replace(
		"/${sx}${sx}${sx}/i",
		"${prime3}",
		$str
	);

	// beginning "
	// [new RegExp(`(${nonWord}|^)"(${word})`, 'g'), '$1\u201c$2'],
	// Using preg_replace_callback to support multiple straight quotes in a row
	$str = preg_replace_callback(
		"/(${nonword}|^)(${dx}+)(${word})/",
		function ($match) use ($d1) {
		    return $match[1].str_repeat($d1, strlen($match[2])).$match[3];
		},
		$str
	);

	// ending "
	// [/(\u201c[^"]*)"([^"]*$|[^\u201c"]*\u201c)/g, '$1\u201d$2'],
	// Using preg_replace_callback to support multiple straight quotes in a row
	$str = preg_replace_callback(
		"/(${d1}[^${dx}]*)(${dx}+)([^${dx}]*$|[^${d1}${dx}]*${d1})/",
		function ($match) use ($d2) {
		    return $match[1].str_repeat($d2, strlen($match[2])).$match[3];
		},
		$str
	);

	// remaining " at end of word
	// [/([^0-9])"/g, '$1\u201d'],
	// Using preg_replace_callback to support multiple straight quotes in a row
	$str = preg_replace_callback(
		"/([^0-9])(${dx}+)/",
		function ($match) use ($d2) {
		    return $match[1].str_repeat($d2, strlen($match[2]));
		},
		$str
	);

	// double prime as two single quotes
	// [/''/g, retainLength => '\u2033' + (retainLength ? '\u2063' : '')],
	$str = preg_replace(
		"/${sx}${sx}/i",
		"${prime2}",
		$str
	);

	// beginning '
	// [new RegExp(`(${nonWord}|^)'(\\S)`, 'g'), '$1\u2018$2'],
	$str = preg_replace(
		"/(${nonword}|^)${sx}([^\s])/",
		"$1${s1}$2",
		$str
	);
	
	// conjunction's possession
	// [new RegExp(`(${word})'([${pL}])`, 'ig'), '$1\u2019$2'],
	$str = preg_replace(
		"/(${word})${sx}(${wcr})/i",
		"$1${s2}$2",
		$str
	);

	// abbrev. years like '93
	// [new RegExp(`(\\u2018)([0-9]{2}[^\\u2019]*)(\\u2018([^0-9]|$)|$|\\u2019[${pL}])`, 'ig'), '\u2019$2$3'],
	$str = preg_replace(
		"/(${s1})([0-9]{2}[^${s2}]*)(${s1}([^0-9]|$)|$|${s2}[${wcr}])/i",
		"${s2}$2$3",
		$str
	);

	// ending '
	// [new RegExp(`((\\u2018[^']*)|[${pL}])'([^0-9]|$)`, 'ig'), '$1\u2019$3'],
	$str = preg_replace(
		"/((${s1}[^']*)|[${wcr}])'([^0-9]|$)/",
		"$1${s2}$3",
		$str
	);

	// backwards apostrophe
	// [new RegExp(`(\\B|^)\\u2018(?=([^\\u2018\\u2019]*\\u2019\\b)*([^\\u2018\\u2019]*\\B${nonWord}[\\u2018\\u2019]\\b|[^\\u2018\\u2019]*$))`, 'ig'), '$1\u2019'],
	// AAAAAAHHHHHH I HAVE NO IDEA WHAT THIS DOES
	$str = preg_replace(
		"/(\\B|^)${s1}(?=([^${s1}${s2}]*${s2}\\b)*([^${s1}${s2}]*\\B${nonword}[${s1}${s2}]\\b|[^${s1}${s2}]*$))/i",
		"$1${s2}$3",
		$str
	);
	
	// double prime
	// [/"/g, '\u2033'],
	$str = preg_replace(
		"/${dx}/i",
		"${prime2}",
		$str
	);
	
	// prime
	//[/'/g, '\u2032']
	$str = preg_replace(
		"/${sx}/i",
		"${prime1}",
		$str
	);

	return $str;
}