[RFC] Add clamp function

[kylekatarnls]

Follow-up #7191

Implementation for the RFC: https://wiki.php.net/rfc/clamp

clamp(2, min: 1, max: 3) // 2
clamp(0, min: 1, max: 3) // 1
clamp(6, min: 1, max: 3) // 3
clamp(2, 1.3, 3.4) // 2
clamp(2.5, 1, 3) // 2.5
clamp(2.5, 1.3, 3.4) // 2.5
clamp(0, 1.3, 3.4) // 1.3
clamp(M_PI, -INF, INF) // 3.141592653589793
clamp(NAN, 4, 6) // NAN
clamp("a", "c", "g") // "c"
clamp("d", "c", "g") // "d"
clamp(new \DateTimeImmutable('2025-08-01'), new \DateTimeImmutable('2025-08-15'), new \DateTimeImmutable('2025-09-15'))->format('Y-m-d') // 2025-08-15
clamp(new \DateTimeImmutable('2025-08-20'), new \DateTimeImmutable('2025-08-15'), new \DateTimeImmutable('2025-09-15'))->format('Y-m-d') // 2025-08-20

clamp(4, 8, 6)
// Throws ValueError: clamp(): Argument #2 ($min) must be smaller than or equal to argument #3 ($max)

clamp(4, NAN, 6)
// Throws ValueError: clamp(): Argument #2 ($min) cannot be NAN

clamp(4, 6, NAN)
// Throws ValueError: clamp(): Argument #3 ($max) cannot be NAN

Documentation: php/doc-en#4814

[medabkari]

The RFC page status is set to Withdrawn, update it to Draft if you have access.