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 logbase 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

    up
    -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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