本文实例讲述了php字符串word末字符实现大小写互换的方法。分享给大家供大家参考。具体实现方法如下：
一、要求：
给出一个字符串如 “a journey of, a thousand 'miles' must can't \begin\ with a single step.” ，通过 php 程序处理变成 “a journey of, a thousand 'miles' must can't begin with a single step.”
这里需要注意：
1、每个单词最后的字符如果是大写就变成小写，如果是小写就变成大写。
2、需要考虑类似  can't 这种形式的转换。
3、标点符号（只考虑 , ' . ;）不用变化。
二、参考算法如下：
代码如下:
    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;
    }
?>
测试代码如下：
代码如下:
//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) .
;
?>
运行结果如下：
代码如下:
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
希望本文所述对大家的php程序设计有所帮助。