范围（-8.00，8.00，0.05），其作用很奇怪

Question

有谁知道为什么范围（-8.00，8.00，0.05），似乎失败了呢？

Array 
(
[0] => -8 
[1] => -7.95 
[2] => -7.9 
[3] => -7.85 
[4] => -7.8 
[5] => -7.75 
[6] => -7.7 
[7] => -7.65 
[8] => -7.6 
[9] => -7.55 
[10] => -7.5 
[11] => -7.45 
[12] => -7.4 
[13] => -7.35 
[14] => -7.3 
[15] => -7.25 
[16] => -7.2 
[17] => -7.15 
[18] => -7.1 
[19] => -7.05 
[20] => -7 
[21] => -6.95 
[22] => -6.9 
[23] => -6.85 
[24] => -6.8 
[25] => -6.75 
[26] => -6.7 
[27] => -6.65 
[28] => -6.6 
[29] => -6.55 
[30] => -6.5 
[31] => -6.45 
[32] => -6.4 
[33] => -6.35 
[34] => -6.3 
[35] => -6.25 
[36] => -6.2 
[37] => -6.15 
[38] => -6.1 
[39] => -6.05 
[40] => -6 
[41] => -5.95 
[42] => -5.9 
[43] => -5.85 
[44] => -5.8 
[45] => -5.75 
[46] => -5.7 
[47] => -5.65 
[48] => -5.6 
[49] => -5.55 
[50] => -5.5 
[51] => -5.45 
[52] => -5.4 
[53] => -5.35 
[54] => -5.3 
[55] => -5.25 
[56] => -5.2 
[57] => -5.15 
[58] => -5.1 
[59] => -5.05 
[60] => -5 
[61] => -4.95 
[62] => -4.9 
[63] => -4.85 
[64] => -4.8 
[65] => -4.75 
[66] => -4.7 
[67] => -4.65 
[68] => -4.6 
[69] => -4.55 
[70] => -4.5 
[71] => -4.45 
[72] => -4.4 
[73] => -4.35 
[74] => -4.3 
[75] => -4.25 
[76] => -4.2 
[77] => -4.15 
[78] => -4.1 
[79] => -4.05 
[80] => -4 
[81] => -3.95 
[82] => -3.9 
[83] => -3.85 
[84] => -3.8 
[85] => -3.75 
[86] => -3.7 
[87] => -3.65 
[88] => -3.6 
[89] => -3.55 
[90] => -3.5 
[91] => -3.45 
[92] => -3.4 
[93] => -3.35 
[94] => -3.3 
[95] => -3.25 
[96] => -3.2 
[97] => -3.15 
[98] => -3.1 
[99] => -3.05 
[100] => -3 
[101] => -2.95 
[102] => -2.9 
[103] => -2.85 
[104] => -2.8 
[105] => -2.75 
[106] => -2.7 
[107] => -2.65 
[108] => -2.6 
[109] => -2.55 
[110] => -2.5 
[111] => -2.45 
[112] => -2.4 
[113] => -2.35 
[114] => -2.3 
[115] => -2.25 
[116] => -2.2 
[117] => -2.15 
[118] => -2.1 
[119] => -2.05 
[120] => -2 
[121] => -1.95 
[122] => -1.9 
[123] => -1.85 
[124] => -1.8 
[125] => -1.75 
[126] => -1.7 
[127] => -1.65 
[128] => -1.6 
[129] => -1.55 
[130] => -1.5 
[131] => -1.45 
[132] => -1.4 
[133] => -1.35 
[134] => -1.3 
[135] => -1.25 
[136] => -1.2 
[137] => -1.15 
[138] => -1.1 
[139] => -1.05 
[140] => -1 
[141] => -0.95000000000002 
[142] => -0.90000000000002 
[143] => -0.85000000000002 
[144] => -0.80000000000002 
[145] => -0.75000000000002 
[146] => -0.70000000000002 
[147] => -0.65000000000002 
[148] => -0.60000000000002 
[149] => -0.55000000000002 
[150] => -0.50000000000002 
[151] => -0.45000000000002 
[152] => -0.40000000000002 
[153] => -0.35000000000002 
[154] => -0.30000000000002 
[155] => -0.25000000000002 
[156] => -0.20000000000002 
[157] => -0.15000000000002 
[158] => -0.10000000000002 
[159] => -0.05000000000002 
[160] => -2.0053403382292E-14 
[161] => 0.04999999999998 
[162] => 0.09999999999998 
[163] => 0.14999999999998 
[164] => 0.19999999999998 
[165] => 0.24999999999998 
[166] => 0.29999999999998 
[167] => 0.34999999999998 
[168] => 0.39999999999998 
[169] => 0.44999999999998 
[170] => 0.49999999999998 
[171] => 0.54999999999998 
[172] => 0.59999999999998 
[173] => 0.64999999999998 
[174] => 0.69999999999998 
[175] => 0.74999999999998 
[176] => 0.79999999999998 
[177] => 0.84999999999998 
[178] => 0.89999999999998 
[179] => 0.94999999999998 
[180] => 0.99999999999998 
[181] => 1.05 
[182] => 1.1 
[183] => 1.15 
[184] => 1.2 
[185] => 1.25 
[186] => 1.3 
[187] => 1.35 
[188] => 1.4 
[189] => 1.45 
[190] => 1.5 
[191] => 1.55 
[192] => 1.6 
[193] => 1.65 
[194] => 1.7 
[195] => 1.75 
[196] => 1.8 
[197] => 1.85 
[198] => 1.9 
[199] => 1.95 
[200] => 2 
[201] => 2.05 
[202] => 2.1 
[203] => 2.15 
[204] => 2.2 
[205] => 2.25 
[206] => 2.3 
[207] => 2.35 
[208] => 2.4 
[209] => 2.45 
[210] => 2.5 
[211] => 2.55 
[212] => 2.6 
[213] => 2.65 
[214] => 2.7 
[215] => 2.75 
[216] => 2.8 
[217] => 2.85 
[218] => 2.9 
[219] => 2.95 
[220] => 3 
[221] => 3.05 
[222] => 3.1 
[223] => 3.15 
[224] => 3.2 
[225] => 3.25 
[226] => 3.3 
[227] => 3.35 
[228] => 3.4 
[229] => 3.45 
[230] => 3.5 
[231] => 3.55 
[232] => 3.6 
[233] => 3.65 
[234] => 3.7 
[235] => 3.75 
[236] => 3.8 
[237] => 3.85 
[238] => 3.9 
[239] => 3.95 
[240] => 4 
[241] => 4.05 
[242] => 4.1 
[243] => 4.15 
[244] => 4.2 
[245] => 4.25 
[246] => 4.3 
[247] => 4.35 
[248] => 4.4 
[249] => 4.45 
[250] => 4.5 
[251] => 4.55 
[252] => 4.6 
[253] => 4.65 
[254] => 4.7 
[255] => 4.75 
[256] => 4.8 
[257] => 4.85 
[258] => 4.9 
[259] => 4.95 
[260] => 5 
[261] => 5.05 
[262] => 5.1 
[263] => 5.15 
[264] => 5.2 
[265] => 5.25 
[266] => 5.3 
[267] => 5.35 
[268] => 5.4 
[269] => 5.45 
[270] => 5.5 
[271] => 5.55 
[272] => 5.6 
[273] => 5.65 
[274] => 5.7 
[275] => 5.75 
[276] => 5.8 
[277] => 5.85 
[278] => 5.9 
[279] => 5.95 
[280] => 6 
[281] => 6.05 
[282] => 6.1 
[283] => 6.15 
[284] => 6.2 
[285] => 6.25 
[286] => 6.3 
[287] => 6.35 
[288] => 6.4 
[289] => 6.45 
[290] => 6.5 
[291] => 6.55 
[292] => 6.6 
[293] => 6.65 
[294] => 6.7 
[295] => 6.75 
[296] => 6.8 
[297] => 6.85 
[298] => 6.9 
[299] => 6.95 
[300] => 7 
[301] => 7.05 
[302] => 7.1 
[303] => 7.15 
[304] => 7.2 
[305] => 7.25 
[306] => 7.3 
[307] => 7.35 
[308] => 7.4 
[309] => 7.45 
[310] => 7.5 
[311] => 7.55 
[312] => 7.6 
[313] => 7.65 
[314] => 7.7 
[315] => 7.75 
[316] => 7.8 
[317] => 7.85 
[318] => 7.9 
[319] => 7.95 
[320] => 8 
) 

Answer 1

这将是因为floating point numbers are not precise而不是所有的数字都可以完全用浮点数表示。

Answer 2

你可能想尝试800和-800之间的范围内的5个步骤，然后在小数点/除以100后添加。

Answer 3

这是一个已知的问题，希望已经固定。见bug #54459。

基本上现在而不是使连续的浮点加法的range函数现在递增的整数，并且由步骤相乘。

基本上，你知道的有：

-8.00, -8.00 + 1 * 0.05, -8.00 + 2 * 0.05, ... 

，而不是

-8.00, -8.00 + 0.05, -8.00 + 0.05 + 0.05, ... 

你可以看到这个有差别：

$ php 
<?php 
for ($i = 0; $i < 9.99; $i += .1) {} 
echo sprintf("%.17f", $i); 
^D 
9.99999999999998046 

同时：

$ php -r 'echo sprintf("%.17f", .1*100);' 
10.00000000000000000