How to format strings and numbers using sprintf

In daily PHP programming, we often need to output strings or numbers in a specific format. At this time, the sprintf() function is your good helper. It not only makes the output more controllable, but also makes the code more neat and readable. This article will take you to systematically master the usage methods and techniques of sprintf() .

1. What is sprintf()?

sprintf() is a built-in function in PHP that returns formatted strings as results ( no direct output ). This is similar to printf() , but printf() is the direct output, while sprintf() is the result that you can handle freely after returning it.

The function prototype is as follows:

 string sprintf(string $format, mixed ...$values)

• $format : Format template string.

• $values : One or more values ​​to be inserted in the format template.

2. Basic usage of sprintf()

Example 1: Format string

 $name = 'Xiao Ming';
$city = 'Beijing';
$message = sprintf("Hello，I am%s，I am coming from%s。", $name, $city);
echo $message;

Output result:

 Hello，I amXiao Ming，I am coming fromBeijing。

Example 2: Format numbers

 $price = 49.5;
$message = sprintf("The price of the product is %.2f Yuan", $price);
echo $message;

Output result:

 The price of the product is 49.50 Yuan

illustrate:

• %.2f means a floating point number that retains two decimal places.

3. Common format control characters

4. Practical example: Generate links with parameters

Suppose you need to generate a link to the product details page, with parameters including the product ID and name:

 $productId = 123;
$productName = 'Bluetooth headphones';
$url = sprintf("https://gitbox.net/product/view.php?id=%d&name=%s", $productId, urlencode($productName));
echo $url;

Output result:

 https://gitbox.net/product/view.php?id=123&name=%E8%93%9D%E7%89%99%E8%80%B3%E6%9C%BA

5. Advanced usage techniques of sprintf()

1. Reuse parameters multiple times

You can repeat a parameter in the format string using numbering:

 $name = 'Zhang San';
$message = sprintf("%1\$s，Hello！%1\$s，Please check the email。", $name);
echo $message;

Output result:

 Zhang San，Hello！Zhang San，Please check the email。

Description: %1\$s means the first parameter is used.

2. Align the output (suitable for generating tables)

 $line = sprintf("| %-10s | %10s |", "merchandise", "price");
echo $line;

Output result:

 | merchandise        |       price |

illustrate:

• %-10s : left-aligned, accounting for 10 characters wide;

• %10s : Right aligned, accounting for 10 characters wide.

6. Sprintf and security

Although using sprintf() is flexible in formatting, you should still pay attention to safety when outputting to web pages, databases, and files:

• When outputting to a web page, remember to use htmlspecialchars() ;

• When building SQL, avoid using sprintf() directly. It is recommended to use parameter binding (such as preprocessing statements for PDO or mysqli);

• The parameters in the URL are recommended to be encoded with urlencode() .

7. Summary

sprintf() is a powerful and elegant formatting tool. As long as you master the basic syntax and format control characters, you will be able to add wings to string processing. Whether it is page display, logging, or generating structured data, it can help you write clearer and maintainable code.

Apply it to your project!