Solved: remove non alphanumeric

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The `[^A-Za-z0-9]` pattern is what is known as a regular expression. It matches any character that is not a letter or a digit.]

The first step in understanding the code is to know the purpose of each element:

preg_replace Function

The `preg_replace` function is used to perform a pattern matching and replacement. It takes three parameters: the pattern to search for, the string to replace it with, and the input string.

Regular Expressions

A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are looking for.

• In this case, we’re using `[^A-Za-z0-9]`.
• The brackets denote a set of characters, but the caret (^) inside the brackets negates the set, meaning it will match any character NOT in the set.
• The A-Za-z0-9 inside the brackets represents all uppercase letters, all lowercase letters, and all numbers.

So `[^A-Za-z0-9]` will match any non-alphanumeric character. And when used with the `preg_replace` function, it will effectively remove all non-alphanumeric characters.

Additional Considerations for SEO and User Experience

If you are generating slugs or otherwise need to preserve spaces, it’s recommended to replace spaces with a character like a hyphen (-) rather than removing them entirely. This can be done with the `str_replace` function:

<?php
  $string = "Hello, World!";
  $string = str_replace(' ', '-', $string); // "Hello,-World!"
  $string = preg_replace("/&#91;^A-Za-z0-9 -&#93;/", '', $string); // "Hello-World"
  echo $string;
?>

This code replaces all the spaces with hyphens first before removing the non-alphanumeric characters, effectively preserving the spaces as hyphens for better readability and SEO.