php man page for readline_completion_function

READLINE_COMPLETION_FUNCTION(3) 					 1					   READLINE_COMPLETION_FUNCTION(3)

readline_completion_function - Registers a completion function

SYNOPSIS
       bool readline_completion_function (callable  $function)

DESCRIPTION
	This function registers a completion function. This is the same kind of functionality you'd get if you hit your tab key while using Bash.

PARAMETERS
	      o $function
		- You must supply the name of an existing function which accepts a partial command line and returns an array of possible matches.

RETURN VALUES
	Returns TRUE on success or FALSE on failure.

PHP Documentation Group 											   READLINE_COMPLETION_FUNCTION(3)