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Validate (input) username

Last updated on by Gabriel Livan

Hello coders,

Here’s a function that validates a username. It can be used when you have a register form and the user should enter a valid username (that shouldn’t contain illegal characters).

<?php
function validate_username($username)
{
$check = eregi_replace('([a-zA-Z0-9_]+)', "", $username);

if(empty($check))
	{
	return true;
	}
	else
	{
	return false;
	}
}

$username = 'john_jones';

$validator = validate_username($username);

if($validator)
{
echo 'The username is valid.';
}
else
{
echo 'The username should contain only letters, numbers and underscores.';
}
?>

If you use ‘john#_$%jones’ as an username the function will return ‘false’.

If you have any comments / suggestions feel free to post them.

Validate numeric string

Last updated on by Gabriel Livan

Check if a string is numeric or not.

<?php
function validate_number($string)
{
if(is_numeric($string))
	{
	return true;
	}
	else
	{
	return false;
	}
}
?>

PHP: How to validate e-mail addresses using regular expressions

Last updated on by Gabriel Livan

This function checks if an email address is valid or not. For example it is very useful if you have to validate a HTML form where someone should enter a real email address.

function ValidateEmail($email)
{
/*
(Name) Letters, Numbers, Dots, Hyphens and Underscores
(@ sign)
(Domain) (with possible subdomain(s) ).
Contains only letters, numbers, dots and hyphens (up to 255 characters)
(. sign)
(Extension) Letters only (up to 10 (can be increased in the future) characters)
*/

$regex = '/([a-z0-9_.-]+)'. # name

'@'. # at

'([a-z0-9.-]+){2,255}'. # domain & possibly subdomains

'.'. # period

'([a-z]+){2,10}/i'; # domain extension 

if($email == '') { 
	return false;
}
else {
$eregi = preg_replace($regex, '', $email);
}

return empty($eregi) ? true : false;
}

$email = '[email protected]'; 

// will return true, since it matches the regex

if(ValidateEmail($email))
{
echo ''.$email.' is a valid e-mail address.';
}
else
{
echo ''.$email.' is not a valid e-mail address.';
}