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  // A valid number is:

  //   1. optional minus sign

  //   2. optional space

  //   3. the rest of the string can't be just a decimal or blank.

  //   3. optional integer portion, with thousands separators

  //   4. optional decimal portion, starting is a decimal separator

  $thousands = $separator ? (preg_quote($separator, '/') . '?') : '';

  $decimal = preg_quote($point, '/');

  return preg_match("/

                    ^               # Start of string

                    -?              # Optional minus sign

                    \ ?             # Optional space

                    (?!\.?$)        # Assert looking ahead, not just a decimal or nothing

                      (?:           # Interger portion (non-grouping)

                        \d{1,3}     #   1 to 3 digits

                        (?:         #   Thousands group(s)

                        $thousands  #     Optional thousands separator

                        \d{2,3}     #     2 or 3 digits. Some countries use groups of 2 sometimes

                      )*            #   0 or more of these thousands groups

                    )?              # End of optional integer portion

                    (?:             # Decimal portion (non-grouping)

                      $decimal      #   Decimal point

                      \d*           #   0 or more digits

                    )?              # End of optional decimal portion

                    $

                    /x", $value);