log

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

log — Natural logarithm

Опис

log(float $num, float $base = M_E): float

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

Параметри

num: The value to calculate the logarithm for
base: The optional logarithmic base to use (defaults to 'e' and so to the natural logarithm).

Значення, що повертаються

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

Прогляньте також

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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User Contributed Notes 1 note

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-4

c0x at mail dot ru ¶

20 years ago

more general version, works fine on negative, very big ($value > 1E+18) and very small ($value < 1E-18) numbers.

function expn($value, $prec = 3, $base = 1000, $prefix = '') {
    $e = array('a', 'f', 'p', 'n', 'u', 'm', '', 'k', 'M', 'G', 'T', 'P', 'E');
    $p = min(max(floor(log(abs($value), $base)), -6), 6);
    return round((float)$value / pow($base, $p), $prec) . $prefx . $e[$p + 6];
}

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