Search and str_replace

[Seven Skins]

I was just wondring can {vb:raw navbits.breadcrumb} be search and replace by using the code below?

PHP Code:

$find = "{vb:raw navbits.breadcrumb}";
$replace = "Joe Blogs";
$myvar = str_replace($find,$replace,$myvar); 


I have been trying to do this but no luck. I can search and replace normal HTML or Text.

Thanks

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