Generate Random String

generateRandomString.php

<?php    
    /**
     * Generate random n-length string
     *
     * Method will generate random string based on given guidelines first parameter is length of returned string,
     * next three parameters define which characters will be used to generate output.
     *
     * @param $length
     * @param bool $alphabetCharacters if set to true, output may contain characters from aA to zZ (65-90 AND 97-122 in ASCII)
     * @param bool $numbersCharacters if set to true, output may contain characters from 0 to 9  (48-57 in ASCII)
     * @param bool $specialCharacters if set to true, output may contain special characters such as !*#,.;&$) etc. (33-47 AND 58-64 AND 91-96 AND 123-126 in ASCII)
     * @return string
     */
    function generateRandomString($length,$alphabetCharacters=true,$numbersCharacters=true,$specialCharacters=true)
    {
        if ($length <= 0){
            throw new \InvalidArgumentException('Output length must be at least 1 character long');
        }

        $availableCharacters=array();
        $randomString='';

        if ($alphabetCharacters){
            $availableCharacters=array_merge($availableCharacters,range(65,90),range(97,122));
        }

        if ($numbersCharacters){
            $availableCharacters=array_merge($availableCharacters,range(48,57));
        }

        if ($specialCharacters){
            $availableCharacters=array_merge($availableCharacters,range(33,47),range(58,64),range(91,96),range(123,126));
        }

        $lowIndex=0;
        $highIndex=count($availableCharacters)-1;

        if ($highIndex === -1){
            throw new \InvalidArgumentException('You must set at least one character group as allowed');
        }

        for($i=1;$i<=$length;$i++){
            $randomString.=chr($availableCharacters[rand($lowIndex,$highIndex)]);
        }

        return $randomString;

    }