smilies_init() WordPress Function

function smilies_init() {
	global $wpsmiliestrans, $wp_smiliessearch;

	// Don't bother setting up smilies if they are disabled.
	if ( ! get_option( 'use_smilies' ) ) {
		return;
	}

	if ( ! isset( $wpsmiliestrans ) ) {
		$wpsmiliestrans = array(
			':mrgreen:' => 'mrgreen.png',
			':neutral:' => "\xf0\x9f\x98\x90",
			':twisted:' => "\xf0\x9f\x98\x88",
			':arrow:'   => "\xe2\x9e\xa1",
			':shock:'   => "\xf0\x9f\x98\xaf",
			':smile:'   => "\xf0\x9f\x99\x82",
			':???:'     => "\xf0\x9f\x98\x95",
			':cool:'    => "\xf0\x9f\x98\x8e",
			':evil:'    => "\xf0\x9f\x91\xbf",
			':grin:'    => "\xf0\x9f\x98\x80",
			':idea:'    => "\xf0\x9f\x92\xa1",
			':oops:'    => "\xf0\x9f\x98\xb3",
			':razz:'    => "\xf0\x9f\x98\x9b",
			':roll:'    => "\xf0\x9f\x99\x84",
			':wink:'    => "\xf0\x9f\x98\x89",
			':cry:'     => "\xf0\x9f\x98\xa5",
			':eek:'     => "\xf0\x9f\x98\xae",
			':lol:'     => "\xf0\x9f\x98\x86",
			':mad:'     => "\xf0\x9f\x98\xa1",
			':sad:'     => "\xf0\x9f\x99\x81",
			'8-)'       => "\xf0\x9f\x98\x8e",
			'8-O'       => "\xf0\x9f\x98\xaf",
			':-('       => "\xf0\x9f\x99\x81",
			':-)'       => "\xf0\x9f\x99\x82",
			':-?'       => "\xf0\x9f\x98\x95",
			':-D'       => "\xf0\x9f\x98\x80",
			':-P'       => "\xf0\x9f\x98\x9b",
			':-o'       => "\xf0\x9f\x98\xae",
			':-x'       => "\xf0\x9f\x98\xa1",
			':-|'       => "\xf0\x9f\x98\x90",
			';-)'       => "\xf0\x9f\x98\x89",
			// This one transformation breaks regular text with frequency.
			//     '8)' => "\xf0\x9f\x98\x8e",
			'8O'        => "\xf0\x9f\x98\xaf",
			':('        => "\xf0\x9f\x99\x81",
			':)'        => "\xf0\x9f\x99\x82",
			':?'        => "\xf0\x9f\x98\x95",
			':D'        => "\xf0\x9f\x98\x80",
			':P'        => "\xf0\x9f\x98\x9b",
			':o'        => "\xf0\x9f\x98\xae",
			':x'        => "\xf0\x9f\x98\xa1",
			':|'        => "\xf0\x9f\x98\x90",
			';)'        => "\xf0\x9f\x98\x89",
			':!:'       => "\xe2\x9d\x97",
			':?:'       => "\xe2\x9d\x93",
		);
	}

	/**
	 * Filters all the smilies.
	 *
	 * This filter must be added before `smilies_init` is run, as
	 * it is normally only run once to setup the smilies regex.
	 *
	 * @since 4.7.0
	 *
	 * @param string[] $wpsmiliestrans List of the smilies' hexadecimal representations, keyed by their smily code.
	 */
	$wpsmiliestrans = apply_filters( 'smilies', $wpsmiliestrans );

	if ( count( $wpsmiliestrans ) == 0 ) {
		return;
	}

	/*
	 * NOTE: we sort the smilies in reverse key order. This is to make sure
	 * we match the longest possible smilie (:???: vs :?) as the regular
	 * expression used below is first-match
	 */
	krsort( $wpsmiliestrans );

	$spaces = wp_spaces_regexp();

	// Begin first "subpattern".
	$wp_smiliessearch = '/(?<=' . $spaces . '|^)';

	$subchar = '';
	foreach ( (array) $wpsmiliestrans as $smiley => $img ) {
		$firstchar = substr( $smiley, 0, 1 );
		$rest      = substr( $smiley, 1 );

		// New subpattern?
		if ( $firstchar != $subchar ) {
			if ( '' !== $subchar ) {
				$wp_smiliessearch .= ')(?=' . $spaces . '|$)';  // End previous "subpattern".
				$wp_smiliessearch .= '|(?<=' . $spaces . '|^)'; // Begin another "subpattern".
			}
			$subchar           = $firstchar;
			$wp_smiliessearch .= preg_quote( $firstchar, '/' ) . '(?:';
		} else {
			$wp_smiliessearch .= '|';
		}
		$wp_smiliessearch .= preg_quote( $rest, '/' );
	}

	$wp_smiliessearch .= ')(?=' . $spaces . '|$)/m';

}