Web Standards Programmer's Reference: HTML, CSS, JavaScript®, Perl, Python®, and PHP

F.30. Program Execution

Function	Returns	Description
exec(string command [, array &output [, int &return_value]])	string	Executes an external program.
system(string command [, int &return_value])	int	Executes an external program and displays output.
passthru(string command [, int &return_value])	void	Executes an external program and displays raw output.
escapeshellcmd(string command)	string	Escapes shell metacharacters.
escapeshellarg(string arg)	string	Quotes and escapes an argument for use in a shell command.
shell_exec(string cmd)	string	Executes command via shell and returns complete output as string.
proc_nice(int priority)	bool	Changes the priority of the current process.
proc_terminate(resource process [, long signal])	int	Kills a process opened by proc_open.
proc_close(resource process)	int	Closes a process opened by proc_open.
proc_get_status(resource process)	array	Gets information about a process opened by proc_open.
proc_open(string command, array descriptorspec, array &pipes [, string cwd [, array env [, array other_options]]])	resource	Runs a process with more control over its file descriptors.