PHP Manual: Bollinger Bands

array trader_bbands(
    array $real,
    int $timePeriod = ?,
    float $nbDevUp = ?,
    float $nbDevDn = ?,
    int $mAType = ?
)

real: Array of real values.
timePeriod: Number of period. Valid range from 2 to 100000.
nbDevUp: Deviation multiplier for upper band. Valid range from TRADER_REAL_MIN to TRADER_REAL_MAX.
nbDevDn: Deviation multiplier for lower band. Valid range from TRADER_REAL_MIN to TRADER_REAL_MAX.
mAType: Type of Moving Average. TRADER_MA_TYPE_* series of constants should be used.

Returns an array with calculated data or false on failure.