Code snippets

Here are some small pieces of code I have done either out of curiosity or simply because I needed it. Most of these codes will seem very basic and easy to advanced PHPers.

Negative number to positive & vice versa

Changing a positive number into a negative and vice versa can be done in one line:

function change_pol($in){
return (0 - $in);
}

Examples:

echo change_pol(1.5); //outputs -1.5
echo change_pol('-2.'); //outputs 2
echo change_pol(0); //outputs 0
echo change_pol(-5 * -34 * 1.98); //outputs -336.6

$test = "-.8";
$test = change_pol($test);
echo $test; //outputs 0.8

If you are using values which cannot be interpreted as numeric values (e.g. change_pol('abc')), 0 will be returned. Even at an error_reporting level of E_ALL, no error is outputted.

GMail address

GMail.Com e-mail addresses can be written in different forms. gmail@gmail.com is the same as gm.ail@googlemail.com, gmAI.l@gmail.com, G.Mail@googlemail.com etc. To prevent users from using the same e-mail address in different variations, put the Gmail address through this code before storing it:

function GMailID($mail){
//see: http://bit.ly/GmailID
    $mail = strtolower($mail);
    $mail = explode('@', $mail);
    if($mail[1] != 'gmail.com' && $mail[1] != 'googlemail.com'){
        return implode('@', $mail);
    }
    $mail[0] = str_replace('.', '', $mail[0]);
    return $mail[0].'@gmail.com';
}

Please be advised that this function might behave oddly or throw error messages if you supply an invalid e-mail address. Please check the input before passing it to GMailID().
Examples of usage:

echo GmailID("G.Mail@GOOGLEmail.com"); //outputs gmail@gmail.com
echo GMailID("GM.ail@GMail.Com"); //outputs gmail@gmail.com
echo GMailID("G.Mail@hotMail.com"); //outputs g.mail@hotmail.com

Highlight PHP

This highlights some PHP code, without the need of the wrapping <?php and ?> tags. (This very function is used on this page.)

Note that this only works for PHP 5. If you are using PHP 4, you will have to change the numbers 79 and -57 as highlight_string() uses the tag <font> (instead of <span>) prior to PHP 5.
Examples of usage:

// it's hard to display the output... try it yourself! ;)
CodeHigh('$test = "string";');
CodeHigh('print_r($_SERVER); phpinfo(); ');

File extension

Detects the file extension from a given string. (Same function as filetype(), except that the supplied argument does not have to be a file but only a string.) This function basically returns the text preceeding the last dot (.).

Note that you should use strtolower() for $ext if you want this function to be case-insensitive.
Examples:

echo filext('test.txt'); // returns 'txt'
$file = 'filename.HTmL';
echo filext($file); // returns 'HTmL'
$var = filext('TES12asd'); // returns false

Anonymize IPs

AnonIP() is a function that allows you to show parts of an IP address in a partially anonymized form. It will output an IP address like 178.162.87.50 as 178.162.76.xx.

Note: Unexpected results are possible if you don't supply a valid IP address. If you aren't sure, try validating your input first. Something like this:

if(preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', $var)){
// $var is a correct IP
}

Examples of usage:

echo AnonIP('124.65.183.320'); // outputs 124.65.183.xxx