<?php
$str='<p style="text-align: center;">
<img style="width: 448px; height: 321px;" src="http://admin.vn/images/images/car_1.jpg" alt="">
</p>';
$search='"';
$replace=''';
$string= str_replace($search,$replace,$str);
echo $string;
?>
echo $string is result no convert from " to ' の場合、修正方法