What is a generator in PHP? how to use?

What is a generator (Generator) in What is a generator in What is a generator in PHP? how to use?? how to use?? how to use? The following article will give you an in-depth explanation of generators in What is a generator in What is a generator in PHP? how to use?? how to use?. I hope it will be helpful to you!

When it comes to driving, speed isn’t everything. But on the web, speed makes all the difference. The faster your application is, the better the user experience is. This article is about What is a generator in What is a generator in PHP? how to use?? how to use? generators, so why are we talking about speed? You'll quickly discover that generators play a huge role in speed and memory management.

What is the What is a generator in What is a generator in PHP? how to use?? how to use? generator?

Generators were added in What is a generator in What is a generator in PHP? how to use?? how to use? 5.5 and provide an easy way to iterate over data without building arrays in memory. Are you a little confused? Then give an example to show that using generators is a good way.

First, create a generator.php file that will be used throughout our example. After creating the file, we add a piece of code.

<?php function getRange ($max = 10) {
    $array = [];

    for ($i = 1; $i < $max; $i++) {
        $array[] = $i;
    }

    return $array;
}

foreach (getRange(15) as $range) {
    echo "Dataset {$range} <br>";
}

We can quickly start a built-in What is a generator in What is a generator in PHP? how to use?? how to use? server in the directory where the generator.php file is created:

php -S localhost:8000

If you use a browser to open http://localhost: 8000/generator.php, we should see a result like this:

This code is not very self-explanatory. Let’s change the code a little bit

<?php foreach (getRange(What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX) as $range) {
    echo "Dataset {$range} <br>";
}

Now, the maximum value that the above code can generate is What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX (that is, the maximum value that What is a generator in What is a generator in PHP? how to use?? how to use? can generate). When we refresh the browser after making this modification, we notice that this time Something is different. This generator script throws a warning message.

Sadly, What is a generator in What is a generator in PHP? how to use?? how to use? runs out of memory. Solutions you can think of might include increasing php.ini The upper limit of memory_limit in the file. But to be fair, this script is both inefficient and takes up memory. What we need is a script that is efficient and takes up low memory.

Using Generators

Let’s define the same function above, call it with the same value What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX and run it again. But this time we will create a generator function.

<?php function getRange ($max = 10) {
    for ($i = 1; $i < $max; $i++) {
        yield $i;
    }
}

foreach (getRange(What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX) as $range) {
    echo "Dataset {$range} <br>";
}

Parsing the getRange function, this time, we only loop through the values ​​and yield output. yield is similar to return value in that it also returns a value from a function, but the only difference is that yield will only return a value when needed and will not try to convert the entire data set remain in memory.

If you go to your browser you should see the data displayed on the page. Given the appropriate time, the browser eventually displays the data.

Note: Generators can only be used within functions.

Why use generators

Sometimes, we may encounter a situation where we want to parse a huge data set (maybe a log file), or the result set of a large database Perform calculations, etc. We don't want all this data to be loaded into memory. We should save the corresponding memory state as much as possible. The data doesn't have to be big - the generator is efficient no matter how small the data is. Don’t forget, our goal is to use less memory to process data as quickly as possible.

Return key-value pairs

Sometimes, our data is more convincing when it is based on key-value. When using a generator, we may generate key-value pairs like the following.

<?php function getRange ($max = 10) {
    for ($i = 1; $i < $max; $i++) {
        $value = $i * mt_rand();

        yield $i => $value;
    }
}

Then, we can use this key-value pair just like any array.

<?php foreach (getRange(What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX) as $range => $value) {
    echo "Dataset {$range} has {$value} value<br>";
}

Pass parameters to the generator

The generator can also receive parameters. This means that the generator allows us to inject parameters into it, as a command or other functions. For example, we send a value to the generator to stop its execution or modify its output. Using the getRange function above, we can achieve this.

<?php function getRange ($max = 10) {
    for ($i = 1; $i < $max; $i++) {
        $injected = yield $i;

        if ($injected === &#39;stop&#39;) return;
    }
}

To send injected this value, we can do this.

<?php $generator = getRange(What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX);

foreach ($generator as $range) {
    if ($range === 10000) {
        $generator->send('stop');
    }

    echo "Dataset {$range} <br>";
}

Note: Using return in the generator will jump out of the generator.

Don’t abuse generators

Although using What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX is a bit over the top. But for me, What is a generator in What is a generator in PHP? how to use?? how to use?_INT_MAX is 2147483647 That is:

Two billion four hundred and seventy-four thousand four hundred and eighty-three thousand six hundred and forty-seven

The generator makes memory usage more efficient. But if abused, it can also cause memory-related problems.

Summary

Generators provide significant performance improvements that are hard to ignore. Most of the time, we don't need a high-configuration server to run the code. We just need to do a little refactoring, generators are very useful and we should use them more

English original address: https://scotch.io/tutorials/understanding-php-generators

Recommended learning: "What is a generator in What is a generator in PHP? how to use?? how to use? Video Tutorial"

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