Error when using str_replace() convert from ' to " - php

Question

<?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;
?>
When I echo $string is result no convert from " to ' , how to fix it

Answer 1

In your original code, you were passing an undefined variable ($str) to the str_replace function
I believe your intention was to pass the $tr variable to the str_replace function.
Also, in your $replace variable, I've changed it to having double quotes (") between the character.
<?php
$tr='<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,$replace,$tr);
echo $string;
?>
Change the $str to $tr as $str is not defined. It will also help if you
Change your $replace to have double quotes
$replace= "'";

Answer 2

You have the text stored in $tr not $str.
<?php
$tr='<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,$replace,$tr); // Changed to $tr
echo $string;
?>
And make sure to escape the ' in $replace='''; (or use "")

Answer 3

$replace='''; is incorrect. You need to escape the second '.
Use either
$replace = "'" so that the single quote does not interfere, or
$replace = '\'' which escapes the middle single quote.

Answer 4

Escape the quote.
$replace='\'';
// or
$replace="'";