PHP/Math/log

calculate logarithms by dividing log() function with log(base)

   <source lang="html4strict">

<?php $val = 100; $i = log($val); echo "log($val) = $i\n"; $i10 = log($val) / log(10); echo "log($val) / log(10) = $i10\n"; $i10 = log10($val); echo "log10($val) = $i10\n"; ?>

 </source>
   
  

Calculate logarithms with other base values by dividing the result of the log() function with log(base).

   <source lang="html4strict">

<?php $val = 100; $i = log($val); echo "log($val) = $i\n"; $i10 = log($val) / log(10); echo "log($val) / log(10) = $i10\n"; $i10 = log10($val); echo "log10($val) = $i10\n"; ?>

 </source>
   
  

Calculation of e, the inverse nature of exp and log

   <source lang="html4strict">

<?php $e = exp(1); echo "$e\n"; $i = log($e); echo "$i\n"; ?>

 </source>