php - insertion through variable in mysql table -

i want insert data mysql table through user defined variables. here doing. gives no error don't upload data table.

$sql="insert table(".$columns_name.") values(".$val.")"; 

here how the values of variables are:
$columns_name= col1, col2, col3, col4
$val= aa, 11, 22, bb

possible issues:

1- table reserved word. table name can't 'table'. (i assume wrote mock name).

2- format of column names , values in insert query wrong.

try before query:

$columns_name = "`$columns_name`"; $columns_name = str_replace(', ', '`, `',$columns_name);  $val = "'$val'"; $val = str_replace(', ', "', '",$val);