(PHP 4, PHP 5, PHP 7, PHP 8)

readline_completion_functionRegisters a completion function


readline_completion_function(callable $callback): bool

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.



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.

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User Contributed Notes 6 notes

chris AT w3style DOT co UK
14 years ago
A little bit of info regarding useful variables when writing your callback function.

There doesn't seem to be a way to set rl_basic_word_break_characters like with the pure C library, so as previous users have pointed out you'll only receive the current word in the input buffer within your callback. If for example you're typing "big bro|ther", where the bar is the position of your cursor when you hit TAB, you'll receive (string) "brother" and (int) 4 as your callback parameters.

However, it is possible (easily) to get more useful information about what the user has typed into the readline buffer. readline_info() is key here. It will return an array containing:

"line_buffer" => (string)
the entire contents of the line buffer (+ some bugs**)

"point" => (int)
the current position of the cursor in the buffer

"end" => (int)
the position of the last character in the buffer

So for the example above you'd get:

* line_buffer => "big brother"
* point => 7
* end => 11

From this you can easily perform multi-word matches.

** NOTE: line_buffer seems to contain spurious data at the end of the string sometime. Fortunately since $end is provided you can substr() it to get the correct value.

The matches you need to return are full words that can replace $input, so your algorithm might crudely look something like:


function your_callback($input, $index) {
// Get info about the current buffer
$rl_info = readline_info();

// Figure out what the entire input is
$full_input = substr($rl_info['line_buffer'], 0, $rl_info['end']);

$matches = array();

// Get all matches based on the entire input buffer
foreach (phrases_that_begin_with($full_input) as $phrase) {
// Only add the end of the input (where this word begins)
// to the matches array
$matches[] = substr($phrase, $index);


cameron at cloudix dot co dot nz
9 years ago
The readline extension can be a bit flakey due to bugs in libedit (PHP 5.3.10-1ubuntu3.15 with Suhosin-Patch (cli) (built: Oct 29 2014 12:19:04)).

I created many segfaults returning an empty array on the autocompletion function:

// Autocomplete
readline_completion_function(function($Input, $Index){

global $Commands;

// Filter Matches
$Matches = array();
foreach(array_keys($Commands) as $Command)
if(stripos($Command, $Input) === 0)
$Matches[] = $Command;

return $Matches;

I found adding an empty string to the matches array prevents the segfault:

// Autocomplete
readline_completion_function(function($Input, $Index){

global $Commands;

// Filter Matches
$Matches = array();
foreach(array_keys($Commands) as $Command)
if(stripos($Command, $Input) === 0)
$Matches[] = $Command;

// Prevent Segfault
if($Matches == false)
$Matches[] = '';

return $Matches;

Hopefully this is helpful to someone.
i dot a dot belousov dot 88 at gmail dot com
8 months ago
If you want to use autocomplete also for history, you can make it like this:

readline_completion_function(function($input, $index) {
$matches = [];

foreach(readline_list_history() as $match)
if (mb_strpos($match, readline_info("line_buffer")) !== false)
$matches[] = mb_substr($match, $index);

return (count($matches) > 1 && $index) ? [] : $matches;
15 years ago
Note: the first argument passed to the registered function is NOT the whole command line as entered by the user, but only the last part, i.e. the part after the last space.

function my_readline_completion_function($string, $index) {
// If the user is typing:
// mv file.txt directo[TAB]
// then:
// $string = directo
// the $index is the place of the cursor in the line:
// $index = 19;

$array = array(

// Here, I decide not to return filename autocompletion for the first argument (0th argument).
if ($index) {
$ls = `ls`;
$lines = explode("\n", $ls);
foreach (
$lines AS $key => $line) {
if (
is_dir($line)) {
$lines[$key] .= '/';
$array[] = $lines[$key];
// This will return both our list of functions, and, possibly, a list of files in the current filesystem.
// php will filter itself according to what the user is typing.
return $array;
john at weider dot cc
21 years ago
It seems that the registered function can accept 2 parameters, the first being the partial string, the second a number that when equal to zero indicates that the tab was hit on the first argument on the input. Otherwise it looks like the position within the string is returned.

This is neccessary information for processing shell command line input.
david at acz dot org
19 years ago
This function can simply return an array of all possible matches (regardless of the current user intput) and readline will handle the matching itself. This is likely to be much faster than attempting to handle partial matches in PHP.
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