src/Util/ComponentUtil.php
public static function fold($string)
    {
        $lines = [];

        if (function_exists('mb_strcut')) {
            while (strlen($string) > 0) {
                if (strlen($string) > 75) {
                    $lines[] = mb_strcut($string, 0, 75, 'utf-8');
                    $string = ' ' . mb_strcut($string, 75, strlen($string), 'utf-8');
                } else {
                    $lines[] = $string;
                    $string = '';
                    break;
                }
            }
        } else {
            $array = preg_split('/(?<!^)(?!$)/u', $string);
            $line = '';
            $lineNo = 0;
            foreach ($array as $char) {
                $charLen = strlen($char);
                $lineLen = strlen($line);
                if ($lineLen + $charLen > 75) {
                    $line = ' ' . $char;
                    ++$lineNo;
                } else {
                    $line .= $char;
                }
                $lines[$lineNo] = $line;
            }
        }

        return $lines;
    }
public static function fold($string)
    {
        $lines = [];

        if (function_exists('mb_strcut')) {
            while (strlen($string) > 0) {
                if (strlen($string) > 75) {
                    $lines[] = mb_strcut($string, 0, 75, 'utf-8');
                    $string = ' ' . mb_strcut($string, 75, strlen($string), 'utf-8');
                } else {
                    $lines[] = $string;
                    $string = '';
                    break;
                }
            }
        } else {
            $array = preg_split('/(?<!^)(?!$)/u', $string);
            $line = '';
            $lineNo = 0;
            foreach ($array as $char) {
                $charLen = strlen($char);
                $lineLen = strlen($line);
                if ($lineLen + $charLen > 75) {
                    $line = ' ' . $char;
                    ++$lineNo;
                } else {
                    $line .= $char;
                }
                $lines[$lineNo] = $line;
            }
        }

        return $lines;
    }
public static function fold ( $ string ) { $ lines = [ ] ; if ( function_exists ( 'mb_strcut' ) ) { while ( strlen ( $ string ) > 0 ) { if ( strlen ( $ string ) > 75 ) { $ lines [ ] = mb_strcut ( $ string , 0 , 75 , 'utf-8' ) ; $ string = ' ' . mb_strcut ( $ string , 75 , strlen ( $ string ) , 'utf-8' ) ; } else { $ lines [ ] = $ string ; $ string = '' ; break ; } } } else { $ array = preg_split ( '/(?<!^)(?!$)/u' , $ string ) ; $ line = '' ; $ lineNo = 0 ; foreach ( $ array as $ char ) { $ charLen = strlen ( $ char ) ; $ lineLen = strlen ( $ line ) ; if ( $ lineLen + $ charLen > 75 ) { $ line = ' ' . $ char ; ++ $ lineNo ; } else { $ line .= $ char ; } $ lines [ $ lineNo ] = $ line ; } } return $ lines ; }
Folds a single line.

According to RFC 5545, all lines longer than 75 characters should be folded

@see https://tools.ietf.org/html/rfc5545#section-5
@see https://tools.ietf.org/html/rfc5545#section-3.1

@param string $string

@return array
Folds a single line .