Functions in PHP8: Various usage scenarios of str_starts_with()

PHP8 is the latest version of the PHP programming language. In this new version, many new functions have been added to the language to help developers write faster, more powerful, and more secure applications. Among them, a very useful function is str_starts_with(), which can be used to determine whether a string starts with a fixed prefix. In this article, we will explore various usage scenarios of str_starts_with() to better understand its value in practical development.

First, let us look at the basic syntax of the str_starts_with() function. Its prototype is as follows:

bool str_starts_with(string $haystack, string $needle)

Among them, $haystack refers to the string to be searched, and $needle is the prefix to be found. The function returns a Boolean value indicating whether the string begins with the specified prefix.

So, when should this function be used? Below are some common usage scenarios.

1. Determine whether the URL starts with the specified prefix

When developing web applications, we often need to check whether the URL starts with a fixed prefix to ensure that the user accesses Correct page. For example, we can use the following code to check whether the URL starts with "/admin/":

$url = $_SERVER['REQUEST_URI'];
if (str_starts_with($url, '/admin/')) {
    // 这是一个管理员页面
} else {
    // 这是一个普通用户页面
}

This code checks whether the currently requested URL starts with "/admin/". If so, it shows an admin page, otherwise it shows a normal user page. This function makes checking URL prefixes very simple and readable.

2. Find the file extension

When processing files, we often need to find the file extension. For example, we can use the following code to get the extension of a file name:

$filename = 'example.txt';
if (str_starts_with($filename, '.')) {
    echo "没有扩展名";
} else {
    $ext = substr(strrchr($filename, '.'), 1);
    echo "扩展名是：$ext";
}

In this example, we first check whether the file name starts with a period. If so, it means the file has no extension. Otherwise, we use the strrchr() function to find the position of the last period in the file name, and use the substr() function to get the file extension from after the period. This function makes finding file extensions very easy.

3. Batch processing strings

Sometimes, we need to batch process multiple strings. For example, we can use an array to store multiple URLs, and then use str_starts_with () function to check whether each URL starts with a specific prefix. For example:

$urls = array(
    'http://example.com/admin/',
    'http://example.com/contact/',
    'http://foo.com/bar/',
    'http://example.com/about/',
);

foreach ($urls as $url) {
    if (str_starts_with($url, 'http://example.com/')) {
        echo "$url 是example.com的页面
";
    } else {
        echo "$url 不是example.com的页面
";
    }
}

In this example, we use an array to store multiple URLs, and then use a foreach loop to iterate through each URL. Within the loop, we use the str_starts_with() function to check if each URL starts with "http://example.com/". If so, output a message indicating that this is the page of example.com. This function makes batch processing of strings very easy.

Conclusion

The str_starts_with() function is a very useful new function in PHP8, which can be used in many different scenarios. In this article, we introduce three common usage scenarios, including determining whether a URL starts with a specified prefix, finding file extensions, and batch processing strings. This function makes string processing easier and more intuitive. If you are a PHP developer, you must understand the usage of this new function.

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