log()
log() — Natural logarithm.
Built-in function of PHP 8.5. The manual lists it as available in PHP 4, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.
What it does
If the optional base parameter is specified, log() returns logbase num, otherwise log() returns the natural logarithm of num.
Signature
log(float $num, float $base = M_E): float
Parameters
| Parameter | Type | What it takes |
|---|---|---|
| $num | float | The value to calculate the logarithm for |
| $base | float | The optional logarithmic base to use (defaults to 'e' and so to the natural logarithm). |
Return value
The logarithm of num to base, if given, or the natural logarithm.
Example
The PHP manual ships no example for log(); the signature and the parameter table above are the contract.
Changelog
| Version | Change |
|---|---|
| 8.0.0 | Now throws a ValueError if base is less than or equal to 0. Previously, an E_WARNING was raised and false was returned. |
See also
log10(), exp(), pow(), error_log()
All PHP 8.5 built-in functions
Reference card built from the PHP manual page log() (PHP documentation, CC BY 3.0). The page is generated from the manual, so the wording of the parameter and return value text follows php.net.