PHP string函数总结
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ceil、floor、round、/、%
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float ceil ( float $value )向上去整（进一） ??? cout(1.8)=>2??? cout(-1.8)=>2-1
float floor ( float $value )向下去整(舍去) ??? floor(1.8)=>1 ??? floor(-1.8)=>-2
round ― 对浮点数进行四舍五入
float round ( float $val [, int $precision ] )??? echo? round ( 1.95583 ,? 2 );?? //?1.96
??? echo? round ( 1241757 ,?- 3 );? //?1242000 =================================