这个函数兼容性太差，WIN下的用了EXEC就不能在LINUX下用了 string exec ( string command [, array output [, int return_var]]) exec() executes the given command, however it does not output anything. It simply returns the last line from the result of the command. If you need to execute a command and have all the data from the command passed directly back without any interference, use the passthru() function. If the array argument is present, then the specified array will be filled with every line of output from the command. Note that if the array already contains some elements, exec() will append to the end of the array. If you do not want the function to append elements, call unset() on the array before passing it to exec(). If the return_var argument is present along with the array argument, then the return status of the executed command will be written to this variable.
string exec ( string command [, array output [, int return_var]])
exec() executes the given command, however it does not output anything. It simply returns the last line from the result of the command. If you need to execute a command and have all the data from the command passed directly back without any interference, use the passthru() function. If the array argument is present, then the specified array will be filled with every line of output from the command. Note that if the array already contains some elements, exec() will append to the end of the array. If you do not want the function to append elements, call unset() on the array before passing it to exec(). If the return_var argument is present along with the array argument, then the return status of the executed command will be written to this variable.