(PHP 4, PHP 5)
log — Natural logarithm
$arg
[, float $base = M_E
] )
If the optional base parameter is specified,
log() returns logbase
arg, otherwise log()
returns the natural logarithm of arg.
arg
The value to calculate the logarithm for
base
The optional logarithmic base to use (defaults to 'e' and so to the natural logarithm).
The logarithm of arg to
base, if given, or the
natural logarithm.
| Version | Description |
|---|---|
| Since 4.3.0 |
The optional parameter base became available.
For older versions you can calculate the logarithm in base b
of a number n, but using the mathematical identity:
logb(n) = log(n)/log(b), where log is the
neperian (or natural) logarithm.
|