Human readable random string for captchas in PHP

CAPTCHAs (Completely Automated Public Turing test to tell Computers and Humans Apart) are challenges designed to differentiate between human users and automated bots. We use them primarily to prevent malicious activities like spam, fake account creation, and denial-of-service attacks on websites. By presenting tasks that are easy for humans to solve but difficult for computers, CAPTCHAs ensure that only legitimate users can access certain online resources.

The below function will generate a human readable string that will look more cose to dictionary words, and this will be useful for captchas.

/************** 
 * @length - length of random string (must be a multiple of 2) 
 **************/  

function readable_random_string($length = 6)
{  
	$conso=array("b","c","d","f","g","h","j","k","l",  
      "m","n","p","r","s","t","v","w","x","y","z");  

	$vocal=array("a","e","i","o","u");  
	$password="";  

	srand ((double)microtime()*1000000);  
	$max = $length/2;  


 	for($i=1; $i<=$max; $i++)  
	{  
		$password.=$conso[rand(0,19)];  
		$password.=$vocal[rand(0,4)];  
	}  
	return $password;  
}