loop like this in php

loop like this in php

for ($i=1; $i<=50; $i++)
{
echo "The number is " . $i . "<br />";
}

i want this type of result in php

utput:
1
2
3
4
5
6
7
8
9
10
[this is ad]
21
22
23
24
25
26
27
28
29
20
[this is ad]
31
32
33
34
35
36
37
38
39
40
[this is ad]
41
42
43
44
45
46
47
48
49
50
[this is ad]

 

Create a variable count and use it to insert ad after each 10 increments.

 

plz can you example?

 

for ($i=1; $i<=50; $i++)
{
echo $i . "<br />";
if ($i % 10 == 0) {
echo "[this is ad]<br />";
}
}