shell_exec 以字符串形式返回所有输出流.exec 默认返回输出的最后一行，但可以将所有输出作为指定为第二个参数的数组提供.

shell_exec returns all of the output stream as a string. exec returns the last line of the output by default, but can provide all output as an array specifed as the second parameter.

见

• http://php.net/manual/en/function.shell-exec.php
• http://php.net/manual/en/function.exec.php