str_replace('"', "", $string);
str_replace("'", "", $string);
I assume you mean quotation marks?
Otherwise, go for some regex, this will work for html quotes for example:
preg_replace("/<!--.*?-->/", "", $string);
C-style quotes:
preg_replace("/\/\/.*?\n/", "\n", $string);
CSS-style quotes:
preg_replace("/\/*.*?\*\//", "", $string);
bash-style quotes:
preg-replace("/#.*?\n/", "\n", $string);
Etc etc...