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
??? 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
??? echo?round(1241757,?-3);?//?1242000
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