Example: validEX($_POST['username'], 'required|alphanum|nospace|len[4,16]');

readme.md

Usage

// RETURN [0] (TRUE | FALSE)
// RETURN [1] (NULL | STRING ERROR MESSAGE)
$validate = validEX($_POST['username'], 'len[6,16]|alphanum|nospace');

// IF [0] IS NOT TRUE, EXIT THE SCRIPT AND RETURNS [1] STRING ERROR MESSAGE
if (!$validate[0]) die($validate[1]);

// OTHERWISE, PROCCEED WITH YOUR SCRIPT

validEX.php

<?php
  function validEX($field, $rules) {
    $rules = explode("|", $rules);

    foreach ($rules as $key => $rule) {
      preg_match_all('/(\w+)[^,\]]?/', $rule, $rule);

      switch ($rule[1][0]) {

        // REQUIRED
        case 'required':
          if ($field == null || empty($field)) {
            return [false, 'This field is required!'];
          }
          break;

        // NO WHITE SPACES
        case 'nospace':
          if (preg_match('/[ ]/', $field)) {
            return [false, 'No white-spaces are allowed!'];
          }
          break;

        // LENGTH
        case 'len':
          if (isset($rule[1][2])) {
            if (strlen($field) < $rule[1][1] || strlen($field) > $rule[1][2]) {
              return [false, "This field must contain between {$rule[1][1]} and {$rule[1][2]} characters. ".strlen($field)." given"];
            }
          } else {
            if (strlen($field) < $rule[1][1] || strlen($field) > $rule[1][1]) {
              return [false, "This field must contain exactly {$rule[1][1]} characters. ".strlen($field)." given"];
            }
          }
          break;
        // ALPHA-NUMERIC CHARACTERS ONLY
        case 'alphanum':
          if (preg_match('/\W /u', $field)) {
            return [false, "Invalid characters found! Only alpha-numeric characters allowed."];
          }
          break;
        // ALPHA CHARACTERS ONLY
        case 'alpha':
          if (preg_match('/[^\p{Latin} ]/u', $field)) {
            return [false, "Invalid characters found! Only alphabetic characters allowed."];
          }
          break;
        // SPECIAL CHARACTERS ALLOWED
        case 'special':
          if (preg_match('/[^\p{Latin}0-9_\-!@#$%&*+~]/iu', $field)) {
            return [false, 'Invalid characters found! A few special characters are allowed! (_-!@#$%&*+~)'];
          }
          break;
        // INTEGER ONLY
        case 'int':
          if (!preg_match('/^(\-|\+)?\d+$/', $field)) {
            return [false, 'This field must contain an integer number.'];
          }
          break;
        // REAL NUMBER
        case 'real':
          if (!preg_match('/^(\-|\+)?\d+(.[\d]+)?$/', $field)) {
            return [false, 'This field must contain a real number.'];
          }
          break;
        // NUMBER RANGE
        case 'range':
            if ($field < $rule[1][1] || $field > $rule[1][2]) {
              return [false, "This field must contain a number between {$rule[1][1]} and {$rule[1][2]}."];
            }
            break;
        // POSITIVE
        case 'pos':
          if ($field < 0) {
            return [false, "This field requires a positive number!"];
          }
          break;
        // MATCH FIELD
        case 'match':
          if ($field != SUBMIT[$rule[1][1]]) {
            return [false, "This field doesn't match the required one."];
          }
          break;
        // EMAIL FIELD
        case 'email':
          if (preg_match('/^[\w.\-]+@[\w.\-]+\.[\w.\-]+$/', $field) == 0) {
            return [false, "A valid email address is required!"];
          }
          break;
        // SUCCESS CASE
        default:
          return [true];
          break;
      }

    }
  }