Generate secure and readable password

generatePassword.php

<?php

public function generate_password($length = 8)
{
    $sets = array();
    $sets[] = 'abcdefghjkmnpqrstuvwxyz';
    $sets[] = 'ABCDEFGHJKMNPQRSTUVWXYZ';
    $sets[] = '23456789';
    $sets[] = '!@#$^*()_.-=';
    $all = '';
    $password = '';

    foreach($sets as $set)
    {
        // Shuffle the string
        $set = str_shuffle($set);
        // And then select the first character of the shuffled string
        $password .= $set[0];
        // Also add the string to $all (for later usage)
        $all .= $set;
    }

    // For remainig character, use $all's characters, randomly
    for($i = 0; $i < $length - count($sets); $i++)
    {
        $all = str_shuffle($all);
        $password .= $all[0];
    }
    $password = str_shuffle($password);
    return $password;
}