replace the empty space with ',' from unicode

[xbl12]

Hi;
I am trying to replace the empty space with the ',' from a string which group by unicode.
I want to have result as following;
?=?','?=?','?=?','?=?','?=?','?=?','?=?','?=?

but my code does not do anything,just give me like the following,could anyone help me, please, thanks.

?=????=????=????=????=????=????=????=?

<?php
mb_internal_encoding("UTF-8");
$search=" ";
$replace="','";
$string="?=????=????=????=????=????=????=????=?";
echo str_ireplace($search,$replace,$string);
?>

 

[xbl12]

Thanks for come here, i have solved out the problem already

 

[Vragabond]

You should let us know how you solved the problem so that someone else can benefit from the solution.

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