autocompleter.php

<?php
error_reporting( -1 );
ini_set( 'display_startup_errors', 1 );
ini_set( 'display_errors', 1 );

$library = [
    'words' => __DIR__ . '/short.txt'
];

function echoAndExit( $msg ) {
    echo json_encode( $msg );
    exit;
}

function setup() {
    $mc = new Memcache;
    if ( $mc->pconnect( "127.0.0.1", 11211 ) ) {
        return $mc;
    }
    $msg = error_get_last();
    echoAndExit( "Problem setting up memcache: " . $msg['message'] );
}

function getMCKey( $val ) {
    return "custom-ac-$val";
}

$mc = setup();

if ( isset( $_GET['flush'] ) ) {
    foreach( $library as $key => $value ) {
        $mc->delete( getMCKey( $key ) );
    }
    echoAndExit( "cache flushed" );
}

if ( !isset( $_GET['l'] ) || !isset( $_GET['f'] ) ) {
    echoAndExit( "Please provide l with the pattern and f with the file." );
}

if ( strlen( $_GET['l'] ) < 3 ) {
    return;
}

$pattern=preg_quote( $_GET['l'], '/' );
$file=$_GET['f'];

if ( !isset( $library[ $file ] ) ) {
    echoAndExit( "Invalid file!" );
}

if ( !is_readable( $library[ $file ] ) ) {
    echoAndExit( "Can't read file!" );
}

$mcKey = getMCKey( $file );
$data = $mc->get( $mcKey, MEMCACHE_COMPRESSED );
if( $data === false ) {
    $data = explode( "\n", file_get_contents( $library[ $file ] ) );

    if ( !is_array( $data ) ) {
        $msg = error_get_last();
        echoAndExit( "Error reading file: " . $msg['message'] );
    }

    if ( false === $mc->set( $mcKey, $data, MEMCACHE_COMPRESSED, 300 ) ) {
        $msg = error_get_last();
        echoAndExit( "Error saving to cache: " . $msg['message'] );
    }
}


$ret = [];
array_map(
    function( $val ) use (&$ret) {
        $ret[] = [
            'title' => $val
        ];
    },
    array_filter( $data,
              function ($line) use ($pattern) {
                  if ( preg_match( "/$pattern/i", $line ) === 1 ) {
                      return true;
                  }
                  return false;
              } ) );

echoAndExit( [ 'pfautocomplete' => $ret ] );