(PHP 5)
proc_nice — Change the priority of the current process
proc_nice() changes the priority of the current process by the amount specified in increment. A positive increment will lower the priority of the current process, whereas a negative increment will raise the priority.
proc_nice() is not related to proc_open() and its associated functions in any way.
The increment value of the priority change.
成功时返回 TRUE， 或者在失败时返回 FALSE. If an error occurs, like the user lacks permission to change the priority, an error of level E_WARNING is also generated.
Note: Availability
proc_nice() will only exist if your system has 'nice' capabilities. 'nice' conforms to: SVr4, SVID EXT, AT&T, X/OPEN, BSD 4.3. This means that proc_nice() is not available on Windows.