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PHP URL validation

/ Published in: PHP
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This function can be used to validate an URL

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  1. <?php
  2.  
  3. function isValidURL($value) {
  4.  
  5. 	$value = trim($value);
  6. 	$validhost = true;
  7.  
  8. 	if (strpos($value, 'http://') === false && strpos($value, 'https://') === false) {
  9. 		$value = 'http://'.$value;
  10. 	}
  11.  
  12. 	//first check with php's FILTER_VALIDATE_URL
  13. 	if (filter_var($value, FILTER_VALIDATE_URL, FILTER_FLAG_HOST_REQUIRED) === false) {
  14. 		$validhost = false;
  15. 	} else {
  16. 		//not all invalid URLs are caught by FILTER_VALIDATE_URL
  17. 		//use our own mechanism
  18.  
  19. 		$host = parse_url($value, PHP_URL_HOST);
  20. 		$dotcount = substr_count($host, '.');
  21.  
  22. 		//the host should contain at least one dot
  23. 		if ($dotcount > 0) {
  24. 			//if the host contains one dot
  25. 			if ($dotcount == 1) {
  26. 				//and it start with www.
  27. 				if (strpos($host, 'www.') === 0) {
  28. 					//there is no top level domain, so it is invalid
  29. 					$validhost = false;
  30. 				}
  31. 			} else {
  32. 				//the host contains multiple dots
  33. 				if (strpos($host, '..') !== false) {
  34. 					//dots can't be next to each other, so it is invalid
  35. 					$validhost = false;
  36. 				}
  37. 			}
  38. 		} else {
  39. 			//no dots, so it is invalid
  40. 			$validhost = false;
  41. 		}
  42. 	}
  43.  
  44. 	//return false if host is invalid
  45. 	//otherwise return true
  46. 	return $validhost;
  47. }
  48.  
  49. ?>

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