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。