How to remove tags from string in php

In web development, string processing is a very common operation, which involves removing HTML tags through regular expressions and other methods. For developers who use PHP to develop, removing HTML tags is a very important skill, because HTML tags will not only affect the display effect of the web page, but may also cause security issues. In this article, we will explore using PHP to remove HTML tags from strings.

1. Use strip_tags function

PHP provides a very simple function strip_tags, which can remove HTML tags by using this function with one line of code. The use of this function is very simple. You only need to pass the string whose label needs to be removed as the first parameter of the function.

The sample code is as follows:

$target_string = "<p>带有HTML标签的字符串</p>";
$result_string = strip_tags($target_string);
echo $result_string; // “带有HTML标签的字符串”

In the above sample code, a string $target_string containing HTML tags is first defined, and then the HTML in the string is removed using PHP's strip_tags function label, and assign the returned result to the $result_string variable, and finally output the result through the echo command.

It should be noted that the strip_tags function will only remove HTML tags by default, and will not remove any other tags, such as XML and PHP tags. If you need not to remove certain tags, you can specify the tags that are allowed to be retained in the second parameter of the function. The input format of this parameter is a string array.

The sample code is as follows:

$target_string = "<p>带有HTML标签的<strong>字符串</strong></p>";
$allow_tags = array("<strong>");
$result_string = strip_tags($target_string, implode("", $allow_tags));
echo $result_string; // “带有HTML标签的<strong>字符串</strong>”

In the above sample code, $allow_tags defines the tags you want to keep. The second parameter of the strip_tags function uses the implode function to splice the elements in the array into String. In the output result, only the HTML tag strong is left.

2. Use the preg_replace function

In addition to using the strip_tags function, you can also use regular expressions in PHP to remove HTML tags. You can use the preg_replace function to achieve this purpose. The preg_replace function can replace the text content in the string. The first parameter of the function is the replacement rule, the second parameter is the replacement content of the first parameter, and the third parameter is the target string, that is, the replacement operation is required. String.

The sample code is as follows:

$target_string = "<p>带有HTML标签的<strong>字符串</strong></p>";
$rule = "/<.*?>/is";
$result_string = preg_replace($rule, '', $target_string);
echo $result_string; // “带有HTML标签的字符串”

In the above sample code, $rule uses a regular expression to match the content inside the angle brackets, that is, the HTML tag. The letter i means to ignore case, and the letter s means to match multi-line strings. Finally, the preg_replace function replaces the matched tag content with an empty string to obtain a result containing only text.

3. Summary of key points

In general, using the strip_tags function can easily complete the task of removing HTML tags, which is very convenient for beginners; using the preg_replace function requires regular expressions Have a certain understanding of formulas and string operations. Strictly speaking, there is no essential difference in the effects achieved by the two methods, but when the application scenarios are different, choosing the appropriate method can improve the maintainability of the code.

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