PHP 出于某种未知原因的语法错误

PHP Syntax Error for some unknown reason

最近开始修复一个旧项目的一些代码,但是我有点生疏了,我这辈子都看不出这段代码有什么问题。据我所知,它看起来不错,但凌晨 3 点 25 分,任何事情都可能出错!

错误:

PHP Parse error:  syntax error, unexpected 'value' (T_STRING), expecting ',' or ';'

代码:

    <?php
if ($post_rank == 0) {
    echo '<option value="0" selected="selected">0</option>';
} else if ($post_rank == 1) {
    echo '<option value="1" selected="selected">1</option>';
} else if ($post_rank == 2) {
    echo '<option value="1" selected="selected" >2</option>';
} else if ($post_rank == 3) {
    echo '<option value="1" selected="selected">3</option>';
} else if ($post_rank == 4) {
    echo '<option value="1" selected="selected">4</option>';
} else if ($post_rank == 5) {
    echo '<option value="1" selected="selected">5</option>';
} else if ($post_rank == 6) {
    echo '<option value="1" selected="selected">6</option>';
} else if ($post_rank == 7) {
    echo '<option value="1" selected="selected">7</option>';
} else if ($post_rank == 8) {
    echo '<option value="1" selected="selected">8</option>';
} else if ($post_rank == 9) {
    echo '<option value="1" selected="selected">9</option>';
} else if ($post_rank == 10) {
    echo '<option value="1" selected="selected">10</option>';
} else if ($post_rank == 11) {
    echo '<option value="1" selected="selected">11</option>';
} else if ($post_rank == 12) {
    echo '<option value="1" selected="selected">12</option>';
} else if ($post_rank == 13) {
    echo '<option value="1" selected="selected">13</option>';
} else if ($post_rank == 14) {
    echo '<option value="1" selected="selected">14</option>';
} else if ($post_rank == 15) {
    echo '<option value="1" selected="selected">15</option>';
}
?>

问题来了,

echo '<option value='0' selected="selected">0</option>';

应该是

echo '<option value="0" selected="selected">0</option>';
                    ^ double quotes.