Remove Non-alphanumeric Characters or Special Characters in PHP

In PHP, there are built-in functions for removing non-alphanumeric characters from strings. The most common function for doing this is preg_replace(). This function takes a regular expression as its first argument and a replacement string as its second argument. The third argument is the string that you want to perform the replacement on. For example, if you wanted to remove all non-alphanumeric characters from a string, you could use the following code:

$str = 'This #string has some @non-alphanumeric characters!';
$str = preg_replace('/[^a-zA-Z0-9]/i', '', $str);
echo $str; // Thisstringhassomenonalphanumericcharacters

$string = 'This is a string with non-alphanumeric characters!@#$%^&*()_+{}[]|:<>?/';
$string = preg_replace('/[^A-Za-z0-9\-]/', '', $string);
echo $string;

As you can see, this code replaces all non-alphanumeric characters with an empty string. This is just one way to use the preg_replace() function for removing non-alphanumeric characters. There are many other ways to do this as well.