mask_email.php

<?php
	
	function mask_email( $email ) {
		/*
		Author: Fed
		Simple way of masking emails
		*/
		
		$char_shown = 3;
		
		$mail_parts = explode("@", $email);
		$username = $mail_parts[0];
		$len = strlen( $username );
		
		if( $len <= $char_shown ){
			return implode("@", $mail_parts );	
		}
		
		//Logic: show asterisk in middle, but also show the last character before @
		$mail_parts[0] = substr( $username, 0 , $char_shown )
			. str_repeat("*", $len - $char_shown - 1 )
			. substr( $username, $len - $char_shown + 2 , 1  )
			;
			
		return implode("@", $mail_parts );
	}

	
	//Sample usage and results
	$emails = array(
		'fed1234@gmail.com'
		, 'veronica@example.co.uk'
		
		, 'fedr@gmail.com'
		, 'fed@gmail.com'
		, 'fe@gmail.com'
		, 'f@gmail.com'
		, 'f@gmail.com'
		
		, 'federicogarcia@gmail.com'
		, 'federico@testing.ph'
		
	
	);
	
	foreach( $emails as $email ){
		echo " <b>$email</b> ";
		echo '<br />';
		
		$em = mask_email ( $email );
		echo $em ;
		echo '<br />';

		echo '<hr />';
		
	}