PHP字符串word末字符实现大小写互换的方法

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：

<?php

    function convertLastChar($str) {

        $markArr = array(", ", "' ", "\" ", ". ", "; ");

        $ret = "";

        for ($i = 0, $j = strlen($str); $i < $j; $i++) {

            if ($i < $j - 2) {

                $afterStr = $str{$i + 1} . $str{$i + 2};

            } else if ($i < $j - 1) {

                $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：

<?php
    //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:<br/>" . $str1 . "<br/>result:<br/>" . convertLastChar($str1) . "<br/><br/>";

    echo "source:<br/>" . $str2 . "<br/>result:<br/>" . convertLastChar($str2) . "<br/><br/>";

    echo "source:<br/>" . $str3 . "<br/>result:<br/>" . convertLastChar($str3) . "<br/><br/>";

    echo "source:<br/>" . $str4 . "<br/>result:<br/>" . convertLastChar($str4) . "<br/><br/>";

    echo "source:<br/>" . $str5 . "<br/>result:<br/>" . convertLastChar($str5) . "<br/><br/>";

    echo "source:<br/>" . $str6 . "<br/>result:<br/>" . convertLastChar($str6) . "<br/><br/>";

?>

运行结果如下：

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。