# log

(PHP 4, PHP 5, PHP 7)

log — Natural logarithm

### Description

log ( float `$arg` [, float `$base` = M_E ] ) : float

If the optional `base` parameter is specified, log() returns logbase `arg`, otherwise log() returns the natural logarithm of `arg`.

### Parameters

`arg`

  The value to calculate the logarithm for

`base`

  The optional logarithmic base to use (defaults to 'e' and so to the natural logarithm).

### Return Values

The logarithm of `arg` to `base`, if given, or the natural logarithm.

### See Also

- log10() - Base-10 logarithm
- exp() - Calculates the exponent of e
- pow() - Exponential expression