Program execution

• escapeshellarg (arg) - Escape a string to be used as a shell argument
• escapeshellcmd (command) - Escape shell metacharacters
• exec (command, output, return_var) - Execute an external program
• passthru (command, return_var) - Execute an external program and display raw output
• proc_close (process) - Close a process opened by proc_open() and return the exit code of that process
• proc_get_status (process) - Get information about a process opened by proc_open()
• proc_nice (increment) - Change the priority of the current process
• proc_open (increment) - Execute a command and open file pointers for input/output
• proc_terminate (process, signal) - Kills a process opened by proc_open
• shell_exec (cmd) - Execute command via shell and return the complete output as a string
• system (command, return_var) - Execute an external program and display the output