for($i=1; $i<100; $i++) { printf("%2d %s\n", $i, preg_match('/^\d?[13579]$/', $i) ? 'yes' : 'no'); } 1 yes 2 no 3 yes 4 no 5 yes 6 no 7 yes 8 no 9 yes 10 no 11 yes 12 no 13 yes 14 no 15 yes 16 no 17 yes 18 no 19 yes 20 no 21 yes 22 no 23 yes 24 no 25 yes 26 no 27 yes 28 no 29 yes 30 no 31 yes 32 no 33 yes 34 no 35 yes 36 no 37 yes 38 no 39 yes 40 no 41 yes 42 no 43 yes 44 no 45 yes 46 no 47 yes 48 no 49 yes 50 no 51 yes 52 no 53 yes 54 no 55 yes 56 no 57 yes 58 no 59 yes 60 no 61 yes 62 no 63 yes 64 no 65 yes 66 no 67 yes 68 no 69 yes 70 no 71 yes 72 no 73 yes 74 no 75 yes 76 no 77 yes 78 no 79 yes 80 no 81 yes 82 no 83 yes 84 no 85 yes 86 no 87 yes 88 no 89 yes 90 no 91 yes 92 no 93 yes 94 no 95 yes 96 no 97 yes 98 no 99 yes
printf("%2d %s\n", $i, preg_match('/^\d?[13579]$/', $i) ? 'yes' : 'no');
}
1 yes
2 no
3 yes
4 no
5 yes
6 no
7 yes
8 no
9 yes
10 no
11 yes
12 no
13 yes
14 no
15 yes
16 no
17 yes
18 no
19 yes
20 no
21 yes
22 no
23 yes
24 no
25 yes
26 no
27 yes
28 no
29 yes
30 no
31 yes
32 no
33 yes
34 no
35 yes
36 no
37 yes
38 no
39 yes
40 no
41 yes
42 no
43 yes
44 no
45 yes
46 no
47 yes
48 no
49 yes
50 no
51 yes
52 no
53 yes
54 no
55 yes
56 no
57 yes
58 no
59 yes
60 no
61 yes
62 no
63 yes
64 no
65 yes
66 no
67 yes
68 no
69 yes
70 no
71 yes
72 no
73 yes
74 no
75 yes
76 no
77 yes
78 no
79 yes
80 no
81 yes
82 no
83 yes
84 no
85 yes
86 no
87 yes
88 no
89 yes
90 no
91 yes
92 no
93 yes
94 no
95 yes
96 no
97 yes
98 no
99 yes
就已经满足了
var_dump(preg_match('/^\d?[13579]$/', 0));//int(0)
var_dump(preg_match('/^\d?[13579]$/', -1));//int(0)
var_dump(preg_match('/^\d?[13579]$/', 100));//int(0)