regular expression

Need to remove all "../" "/.." from user inputing string to prevent him walking and creating files&directories where I don't whant see them/him... The string: $path = eregi_replace('([..]{2,})|([./]{2})|([../]{3,})|([/.]{2})|([/..]{3})', '', $path); works good with any combinations ( ../../..qwert.txt => qwert.txt) untill somth like "/../asd/../qwert.txt" will be entered ... (/../asd/../qwert.txt => asdqwert.txt). So the qwestion is how upgrade regular expression to remove all this correctly (with all entered directory names but NOT assigned their names to file name... Must do the operation: /../asd/......../qwert.txt => qwert.txt but not => /asd/qwert.txt or asdqwert.txt.ru or /................../asd/../qwert.txt.ru => qwert.txt.ru but not => /asd/qwert.txt.ru or asdqwert.txt.ru Thanks.