How to use Elasticsearch technology in PHP?

With the rise of Web applications, search engines have become an essential feature of modern applications. In the past, we used SQL queries to search data, but SQL was not designed specifically for searching. In order to make up for this shortcoming, full-text search engines were created, such as Apache Solr, Elasticsearch, etc.

Elasticsearch is a popular Lucene-based full-text search engine that provides out-of-the-box distributed search and analysis capabilities for real-time data analysis and search engines. Compared with traditional relational databases, Elasticsearch can perform queries faster, can better handle highly dynamic data structures, and supports richer query languages.

In this article, we will introduce how to use Elasticsearch in PHP applications.

Environment preparation

First, we need to install Elasticsearch on the local environment or remote server. Elasticsearch supports all common operating systems, including Windows, macOS, and Linux. You can get various versions of the installer on the official website, or you can use the package manager to install it.

In order to use PHP's elasticsearch client library, we also need to install PHP's elasticsearch client extension. It can be downloaded and compiled and installed via PECL or manually. The following is an example of using PECL:

pecl install elasticsearch

Then add the following line in php.ini:

extension=elasticsearch.so

After the installation is complete, we can use PHP to operate Elasticsearch.

Using Elasticsearch in PHP

Using Elasticsearch in PHP requires using an Elasticsearch client class or library. Currently, there are many PHP Elasticsearch client libraries available, including Elasticsearch-PHP, Elasticsearch-DSL, and Elastica, among others.

In this article, we will use the Elasticsearch-PHP library to demonstrate the use of Elasticsearch.

First, we need to create an Elasticsearch client object:

$client = ElasticsearchClientBuilder::create()->build();

Now, we can use this client object to establish a connection with Elasticsearch and perform various operations.

Indexing and searching documents

In Elasticsearch, documents refer to data in JSON format. Using the PHP Elasticsearch client library, we can easily convert PHP arrays to JSON format and index them into Elasticsearch. First, we need to select an index (similar to a table in a relational database) and then add data to that index.

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'id' => '1',
    'body' => ['title' => 'My first document', 'content' => 'Hello World']
];
$response = $client->index($params);

In the above code, we used the index method to index the document. The index method requires a parameter array containing at least the following keys:

• index: The name of the index
• type: Type of document
• id: Unique identifier of the document
• body: Array or JSON format string containing document data

The above code example creates an index named my_index, of type my_type, with a document unique identifier of 1, and contains a title and content fields. Once the documents are indexed and stored in Elasticsearch, we can search them.

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'title' => 'My first document'
            ]
        ]
    ]
];
$response = $client->search($params);

In the above code, we use the search method to search for documents. The search method requires an argument array containing at least the following keys:

• index: The name of the index to search
• type: The type of document to search for
• body: The array containing the actual search query

The above code example searched for my_index In the index, documents of type my_type and title contain My first document. The search result is a JSON-formatted response containing documents matching the query.

Paging and Sorting

When the search result set is large, we may want to paginate or sort the results. We can use the parameters provided by Elasticsearch to achieve these two functions.

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'query' => [
            'match' => [
                'title' => 'document'
            ]
        ]
    ],
    'size' => 10,
    'from' => 0,
    'sort' => ['title' => ['order' => 'asc']]
];
$response = $client->search($params);

In the above code, we added the following additional parameters:

• size: The number of documents per page
• from: The position of the starting document, used for paging
• sort: Sort in ascending order by the title field

The above example obtains the first 10 documents matching document and sorts them in ascending order by the title field.

Aggregation Search

Elasticsearch also supports aggregate search, a technique that performs various analyzes on a search result set. For example, we can extract all unique values ​​for the author field from the search results.

$params = [
    'index' => 'my_index',
    'type' => 'my_type',
    'body' => [
        'aggs' => [
            'unique_authors' => [
                'terms' => [
                    'field' => 'author.keyword',
                    'size' => 10
                ]
            ]
        ]
    ]
];
$response = $client->search($params);

In the above code, we use aggs as the new key in the parameter array and define an aggregate search named unique_authors in it. terms means that we will group and aggregate based on the value of the author field. The field key is used to specify the field to be aggregated, and the size key specifies the size limit of the aggregated grouping.

in conclusion

Elasticsearch is a powerful full-text search engine that has become an indispensable part of many modern web applications. It can help us better process data and conduct real-time searches. This article explains how to use Elasticsearch in PHP and how to index, search, paginate, and sort documents. In addition, it also introduces how to use Elasticsearch for aggregate search. Now, you have learned how to use Elasticsearch to implement efficient and fast searches in your PHP applications.

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