记一次浮点数比较

<?php
echo "<br>";
printf ( "%01.53f" ,  0.8 );//53位小数表示0.8
echo "<br>";
echo "<br>";
echo "<br>";
echo "<br>";
printf ( "%01.53f" ,  round(0.1+0.7,15) );//精确到15位小数
echo "<br>";
printf ( "%01.53f" ,  round(0.8,15) );//精确到15位小数

echo "<br>";
printf ( "%01.53f" ,  (0.1+0.7) );
echo "<br>";
printf ( "%01.53f" ,  0.8 );
echo "<br>";
var_dump(round(0.1+0.7,15)==round(0.8,15));//如果精确到小数点后15为,则看第16位,是9,所以进1,所以和0.8相同

echo "<br>";
printf ( "%01.53f" ,  (0.2+0.7) );
echo "<br>";
printf ( "%01.53f" ,  0.9 );
echo "<br>";
var_dump(round(0.2+0.7,16)==round(0.9,16));