PROBLEM:

• How to remove non-alphanumeric characters from a string

SOLUTION 1:

•  To remove non-alphanumeric characters from a string,first you need to basically defined it as a regex.

preg_replace("/[^A-Za-z0-9 ]/", '', $string);

SOLUTION 2:

• For unicode characters, we have to use the below example:

 preg_replace("/[^[:alnum:][:space:]]/u", '', $string);

SOLUTION 3:

• We can also use the regular expression.

   Here is an example:

$str = preg_replace('/[^a-z\d ]/i', '', $str);

we need to  note of the following

• The i stands for case insensitive.
• ^ means, does not start with.
• \d matches any digit.
• a-z matches all characters between a and z. Because of the i parameter you don’t have to specify a-z and A-Z.
• After \d there is a space, so spaces are allowed in this regex

SOLUTION 4:

• here’s a really simple regex for remove non-alpha numeric characters:

  \W|_

and used as you need it (with a forward / slash delimiter).

 preg_replace("/\W|_/", '', $string);

• Test it here with this great tool that explains what the regex is doing:

http://www.regexr.com/

SOLUTION 5:

• A PHP function that strips a string of all characters other than alphanumeric characters:

function onlyAlphanumericAndSpaces($text) 
{
  # allow only alphanumeric
  return ereg_replace("[^A-Za-z0-9 ]", "", $text );
}

SOLUTION 6:

• We can also use the below code to Remove All Non-Numeric Characters

/**
* Remove all characters except numbers.
*
* @param string $string
* @return string
*/
function stripNonNumeric( $string ) 
{
    return preg_replace( "/[^0-9]/", "", $string );
}

SOLUTION 7:

• This code will delete any non-alphanumeric characters specified between the brackets, and then output/return the clean version.

The code:

<?php $string = "Here! is some text, and numbers 12345, and symbols !£$%^&";
$new_string = preg_replace("/[^a-zA-Z0-9\s]/", "", $string);
echo $new_string ?>