String Validation
Validate name, surname by the below function to restrict only letters and spaces.

function validateString($str)
{
//accept letters and space only
return preg_match('/^[A-Za-zs ]+$/', $str);
}

Validate numeric value by the below function to restrict only numbers,you can uncomment any line according to your need.

function validateNumber($value)
{
//is_double($value);
//is_float($value);
//is_int($value);
//is_integer($value);
return is_numeric($value);
}

Alphanumeric Characters Validation
Below function validates alphanumeric characters.ctype is complete function library in PHP.

function validateAlphanumeric($string)
{
return ctype_alnum ($string);
}

Validation for URL Exist or not
This function will check whether a given URL exist and not only validate it.

function urlExist($url)
{
$url = @parse_url($url);
if (!$url){
return false;
}
$url = array_map('trim', $url);
$url['port'] = (!isset($url['port'])) ? 80 : (int)$url['port'];
$path = (isset($url['path'])) ? $url['path'] : '';

if ($path == ''){
$path = '/';
}
$path .= (isset($url['query'])) ? '?$url[query]' : '';
if (isset($url['host']) AND $url['host'] != @gethostbyname($url['host']))
{
if (PHP_VERSION >= 5){
$headers = @get_headers('$url[scheme]://$url[host]:$url[port]$path');
}else{
$fp = fsockopen($url['host'], $url['port'], $errno, $errstr, 30);
if (!$fp){
return false;
}
fputs($fp, 'HEAD $path HTTP/1.1rnHost: $url[host]rnrn');
$headers = fread($fp, 4096);
fclose($fp);
}
$headers = (is_array($headers)) ? implode('n', $headers) : $headers;
return (bool)preg_match('#^HTTP/.*s+[(200|301|302)]+s#i', $headers);
}
return false;
}

Validation for check Image Exist
Below function will check whether a given image link exist and not.

function imageExist($url) {
if(@file_get_contents($url,0,NULL,0,1)){return 1;}else{ return 0;}
}

IP Address Validation
function will validate an IP address.

function validateIP($IP){
return preg_match('/^(([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$/',$IP)
}

Validation for Proxy
This function will detect proxy visitors even those that are behind anonymous proxy 🙂

function validateProxy(){
if ($_SERVER['HTTP_X_FORWARDED_FOR']
|| $_SERVER['HTTP_X_FORWARDED']
|| $_SERVER['HTTP_FORWARDED_FOR']
|| $_SERVER['HTTP_VIA']
|| in_array($_SERVER['REMOTE_PORT'], array(8080,80,6588,8000,3128,553,554))
|| @fsockopen($_SERVER['REMOTE_ADDR'], 80, $errno, $errstr, 30))
{
exit('Proxy detected');
}
}

Strong Password Validation
Check whether a particular password filled by the user is strong enough or not.

function validatePassword($password){
//must contain 8 characters, 1 uppercase, 1 lowercase and 1 number
return preg_match('/^(?=^.{8,}$)((?=.*[A-Za-z0-9])(?=.*[A-Z])(?=.*[a-z]))^.*$/', $password);
}

Credit Card Validation
Below function validate credit card number format.

function validateCreditCard($cc){
//eg. 746486033718121
return preg_match('/^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})$/', $cc);
}