PHP字符串word末字符实现大小写互换的方法，字符串大小写_PHP教程

    function convertLastChar($str) {
        $markArr = array(", ", "' ", "\" ", ". ", "; ");
        $ret = "";
        for ($i = 0, $j = strlen($str); $i             if ($i                 $afterStr = $str{$i + 1} . $str{$i + 2};
            } else if ($i                 $afterStr = $str{$i + 1} . " ";
            }
            if (in_array($afterStr, $markArr)
                || $i == $j - 1
                || $str{$i + 1} == " ") {
                $ret .= strtoupper($str{$i}) === $str{$i}
                    ? strtolower($str{$i})
                    : strtoupper($str{$i});
            } else {
                $ret .= $str{$i};
            }
        }
        return $ret;
    }
?>

    //test
    $str1 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step.";
    $str2 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step. ";
    $str3 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step. a ";
    $str4 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step. a B";
    $str5 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step. a b'";
    $str6 = "A journey of, a thousand 'miles' must can't \"begin\" with a single step. a B\"";

    echo "source:
" . $str1 . "
result:
" . convertLastChar($str1) . "

";
    echo "source:
" . $str2 . "
result:
" . convertLastChar($str2) . "

";
    echo "source:
" . $str3 . "
result:
" . convertLastChar($str3) . "

";
    echo "source:
" . $str4 . "
result:
" . convertLastChar($str4) . "

";
    echo "source:
" . $str5 . "
result:
" . convertLastChar($str5) . "

";
    echo "source:
" . $str6 . "
result:
" . convertLastChar($str6) . "

";
?>

source:
A journey of, a thousand 'miles' must can't "begin" with a single step.
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP.

source:
A journey of, a thousand 'miles' must can't "begin" with a single step.
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP.

source:
A journey of, a thousand 'miles' must can't "begin" with a single step. a
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP. A

source:
A journey of, a thousand 'miles' must can't "begin" with a single step. a B
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP. A b

source:
A journey of, a thousand 'miles' must can't "begin" with a single step. a b'
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP. A B'

source:
A journey of, a thousand 'miles' must can't "begin" with a single step. a B"
result:
a journeY oF, A thousanD 'mileS' musT can'T "begiN" witH A singlE steP. A b"