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In PHP, the preg_replace_callback_array function is a powerful tool that executes a callback function to replace it when a regular expression matches a specific pattern. It can handle complex string replacement operations, especially when you want to handle multiple patterns and callback functions, it provides a more concise and efficient way.
This article will explain how to use preg_replace_callback_array to convert custom tags to HTML elements. Suppose we have a custom tag with a format similar to [custom_tag] , which we want to convert into a standard HTML element (e.g. <div> ).
First, we need to understand the basic usage of preg_replace_callback_array . The syntax of this function is as follows:
preg_replace_callback_array(array $patterns_and_callbacks, string $subject);
$patterns_and_callbacks : is an associative array containing regular expressions and callback functions. Each regular expression is applied to the input string, and the corresponding callback function is executed when matched.
$subject : is the input string to match and replace.
Suppose our task is to convert the following custom tags into HTML elements:
[custom_tag] Convert to <div class="custom-tag"> tag
[another_tag] Convert to <span class="another-tag"> tag
Next, we write the code to complete this transformation using preg_replace_callback_array :
<?php
// Enter string，Include custom tags
$input_string = "This is a included[custom_tag]Label[/custom_tag]and[another_tag]Label[/another_tag]Examples。";
// 定义正则表达式and回调函数
$patterns_and_callbacks = [
'/\[custom_tag\](.*?)\[\/custom_tag\]/s' => function ($matches) {
return "<div class='custom-tag'>" . htmlspecialchars($matches[1]) . "</div>";
},
'/\[another_tag\](.*?)\[\/another_tag\]/s' => function ($matches) {
return "<span class='another-tag'>" . htmlspecialchars($matches[1]) . "</span>";
}
];
// use preg_replace_callback_array Make a replacement
$result = preg_replace_callback_array($patterns_and_callbacks, $input_string);
// Output result
echo $result;
?>
The first parameter of preg_replace_callback_array is an associative array that contains regular expressions and corresponding callback functions. When the regular expression matches the [custom_tag] or [another_tag] tag, the corresponding callback function is called.
In the callback function, we use the htmlspecialchars function to escape the tag content to prevent XSS attacks.
Finally, the HTML element returned by the callback function is replaced with the original custom tag.
Assume that the input string is:
This is a included[custom_tag]Label[/custom_tag]and[another_tag]Label[/another_tag]Examples。
After executing the above code, the output will be:
This is a included<div class='custom-tag'>Label</div>and<span class='another-tag'>Label</span>Examples。
preg_replace_callback_array is a powerful tool that simplifies scenarios that require multiple regular replacement operations. In this example, we successfully converted the custom tags [custom_tag] and [another_tag] into HTML elements <div> and <span> .
If you need to deal with more complex label conversions, you can extend the logic of the callback function according to your needs. By using this function reasonably, you can easily deal with various string replacement and processing tasks.
