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log

(PHP 4, PHP 5, PHP 7, PHP 8)

log — Natural logarithm

Description

If the optional base parameter is specified, log() returns log_base num, otherwise log() returns the natural logarithm of num.

Parameters

num

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 num to base, if given, or the natural logarithm.

Errors/Exceptions

Throws a ValueError if base is less than or equal to 0.

Changelog

Version	Description
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() - Base-10 logarithm
• exp() - Calculates the exponent of e
• pow() - Exponential expression
• error_log() - Send an error message to the defined error handling routines

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