PHP convert characters to HTML entities

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PHP Convert characters to HTML entities

HTML entities are codes used to represent special characters that cannot be typed directly in HTML. php provides a variety of built-in functions that convert characters into their corresponding HTML entities to ensure that special characters are displayed correctly on web pages.

htmlentities() function

The

htmlentities() function is the most commonly used function for converting characters into HTML entities. It accepts the string to be converted as the first parameter and returns the converted string. This function can also specify the encoding for conversion, which defaults to UTF-8.

$string = "I"m a &programmer";
$encodedString = htmlentities($string);
// Output: I"m a &programmer

htmlspecialchars() function

The

htmlspecialchars() function is similar to the htmlentities() function, but it only converts certain predefined HTML special characters, such as &, <, > and " .This prevents script attacks because malicious users cannot inject unwanted HTML code.

$string = "<script>alert("XSS attack")</script>";
$encodedString = htmlspecialchars($string);
// Output:<script>alert("XSS attack")</script>

html_entity_decode() function

html_entity_decode() The function performs the opposite operation of htmlentities(), converting HTML entities into corresponding characters.

$string = "&";
$decodedString = html_entity_decode($string);
// Output: &

Customized filtering

In addition to the built-in functions, you can also define your own custom filtering to convert specific characters into HTML entities. This can be achieved by using the filter_var() function.

$filter = FILTER_CALLBACK;
$callback = function ($char) {
switch ($char) {
case "&":
return "&";
case "<":
return "<";
case ">":
return ">";
default:
return $char;
}
};
$string = "I"m a &programmer";
$encodedString = filter_var($string, $filter, ["options" => ["callback" => $callback]]);
// Output: I"m a &programmer

Choose the right function

Choosing which function to use depends on your specific needs. For general text conversion, the htmlentities() function is the best choice. For preventing script attacks, the htmlspecialchars() function is more suitable. If you need custom filtering, you can use the filter_var() function.

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