(PHP 4, PHP 5, PHP 7)
bcsqrt — Get the square root of an arbitrary precision number
$operand
   [, int $scale = 0
  ] ) : string
   Return the square root of the operand.
  
operandThe operand, as a string.
scaleThis optional parameter is used to set the number
of digits after the decimal place in the result. If omitted, it will default to the scale set
globally with the bcscale() function, or fallback to 0 if
this has not been set.
   Returns the square root as a string, or NULL if 
   operand is negative. 
  
Example #1 bcsqrt() example
<?php
echo bcsqrt('2', 3); // 1.414
?>