title: How to generate unique secure random string in PHP?
body: <p>I want to add random string as token for form submission which is generated unique forever. I have spent to much time with Google but I am confused which combination to use?</p>
  
  <p>I found so many ways to do this when I googled:</p>
  
  <pre><code>1) Combination of character and number.
  
  2) Combination of character, number and special character.
  
  3) Combination of character, number, special character and date time.
  </code></pre>
  
  <p>Which combination may i use?</p>
  
  <p>How many character of random string may I generate.?</p>
  
  <p>Any other method which is secure then please let me know.?</p>