Functions in PHP8: Various specific applications of str_starts_with()

With the release of PHP8, many new functions and language features have been introduced, one of the very useful functions is str_starts_with(). It can be used to determine whether a string starts with a specified prefix, which is very useful for processing strings. In this article, we will explore various specific applications of the str_starts_with() function and demonstrate how to use it in real-world applications.

1. Check file type
   str_starts_with() function can be used to check file type. For example, we can use the str_starts_with() function to determine whether a file name begins with "image/" to determine whether the file is an image file. Here is a sample code:

$file = "image/my_image.png";
if (str_starts_with($file, "image/")) {
    echo "This file is an image";
} else {
    echo "This file is not an image";
}

If the $file string starts with "image/", then it is an image file, if not, it is not.

2. Filter input string
   In actual web applications, we need to filter user input data to ensure security and reliability. We can use the str_starts_with() function to filter some suspicious values ​​​​in the string.

For example, we can use the str_starts_with() function to check if the email address in the form submission starts with the @ symbol. Here is a sample code:

$email = $_POST['email'];
if (str_starts_with($email, "@")) {
    echo "Invalid email address";
} else {
    echo "Valid email address";
}

If the $email string starts with "@", it means it is not a valid email address.

3. Constructing URL
   The str_starts_with() function is very useful when constructing a URL. For example, we can use this to check if a URL starts with http:// or https:// to make sure it is a valid URL.

The following is a sample code that demonstrates how to use the str_starts_with() function to build a URL:

$url = "http://www.example.com";
if (!str_starts_with($url, "http://") && !str_starts_with($url, "https://")) {
    $url = "http://" . $url;
}
echo $url;

In this example, if the entered URL does not end with http:// or https: //, then http:// will be added before the URL to ensure that it is a valid URL.

4. Compare strings
   The str_starts_with() function is very useful when multiple strings need to be compared. For example, we can use it to compare multiple URLs or email addresses and group them into different categories based on whether the strings start with the same prefix.

The following is a sample code that compares multiple URLs:

$url1 = "http://www.example.com";
$url2 = "https://www.example.com";
$url3 = "http://www.google.com";
if (str_starts_with($url1, "http://")) {
    echo "URL1 is an HTTP URL";
}
if (str_starts_with($url2, "http://")) {
    echo "URL2 is an HTTP URL";
}
if (str_starts_with($url3, "http://")) {
    echo "URL3 is an HTTP URL";
} else {
    echo "URL3 is not an HTTP URL";
}

In this example, we check whether each URL starts with "http://" through the str_starts_with() function to determine if they are HTTP URLs.

Summary
In this article, we learned about the newly added str_starts_with() function in PHP8 and its various specific applications. From checking file types, filtering input, building URLs to comparing strings, the str_starts_with() function is extremely useful when working with strings. These examples are just a few examples of the str_starts_with() function, and other methods similar to this can be considered as a way to implement the above examples.

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