Decode html special chars and other elements

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How to convert in PHP elements like \[code\]à\[/code\] and \[code\]’\[/code\] to a default utf8 character?I try html_entity_decode with no success (i display some \[code\]?\[/code\] in place of the \[code\]à\[/code\] and \[code\]’\[/code\] in place of \[code\]’\[/code\])