PHP: need explanation using [a-zA-Z0-9]
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I am new to PHP (not programming overall), and having problems with this simple line of code. I want to check whether some input field has been filled as anysymbolornumber@anysymbolornumber just for checking whether correct email was typed. I don't get any error, but the whole check system doesn't work. Here is my code and thanks!

  

      if ($email = "[a-zA-Z0-9]@[a-zA-Z0-9]")
    {