A Method for Realizing Case Interchange of PHP End Character of word String

In this paper, the case exchange method of PHP string word end character is described. Share it for your reference. The specific implementation method is as follows:

1. Requirements:
A string such as "A journey of, a thousand 'miles' must can 't\" begin\ "with a single step." is given, which is processed by PHP program into "a ES22oF, A thousanD' mileS 'musT can' T" begiN "witH A singlE steP."

Note here:

1. The last character of each word becomes lowercase if it is uppercase, and becomes uppercase if it is lowercase.
2. Transformations like can 't need to be considered.
3. Punctuation marks (only consider, '".;) No change.

2. The reference algorithm is as follows:

<?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;

    }

?>

The test code is as follows:

<?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/>";

?>

The running results are as follows:

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"

I hope this article is helpful to everyone's PHP programming.