# PHP Exercises: Test if circumference of two circles intersect or overlap

## PHP: Exercise-58 with Solution

There are two circles C1 with radius r1, central coordinate (x1, y1) and C2 with radius r2 and central coordinate (x2, y2)

Write a PHP program to test the followings -

"C2 is in C1" if C2 is in C1

"C1 is in C2" if C1 is in C2

"Circumference of C1 and C2 intersect" if circumference of C1 and C2 intersect, and and
"C1 and C2 do not overlap" if C1 and C2 do not overlap.

**Input:**Input numbers (real numbers) are separated by a space.

Input 0 to exit.

**Sample Solution: **

**PHP Code:**

```
<?php
// Read the number of test cases from standard input
$n = intval(fgets(STDIN));
// Loop through each test case
for ($i = 0; $i < $n; $i++) {
// Read the coordinates and radii of two circles from standard input
fscanf(STDIN, "%lf %lf %lf %lf %lf %lf", $xa, $ya, $ra, $xb, $yb, $rb);
// Calculate the distance between the centers of the two circles
$r = sqrt(($xb - $xa) * ($xb - $xa) + ($yb - $ya) * ($yb - $ya));
// Check if one circle is completely inside the other
if ($r + $ra < $rb) {
echo "C1 is in C2\n";
continue;
}
if ($r + $rb < $ra) {
echo "C2 is in C1.\n";
continue;
}
// Check if the circumferences of the circles intersect
if ($r <= $ra + $rb) {
echo "Circumference of C1 and C2 intersect.\n";
continue;
}
// Circles do not overlap or intersect
echo "C1 and C2 do not overlap.\n";
}
?>
```

**Sample Input:**

2

0.0 0.0 6.0 0.0 0.0 5.0

0.0 0.0 3.0 5.1 0.0 3.0

Sample Output:

C2 is in C1. Circumference of C1 and C2 intersect.

**Flowchart: **

**PHP Code Editor:**

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