Predefined Constants

The constants below are always available as part of the PHP core.

Mathematical Constants

M_PI (float)

Approximation of the number π (pi). (3.14159265358979323846).

M_E (float)

Approximation of Euler's number e (2.7182818284590452354).

M_LOG2E (float)

Approximation of log2(e) (1.4426950408889634074).

M_LOG10E (float)

Approximation of log10(e) (0.43429448190325182765).

M_LN2 (float)

Approximation of ln(2) (0.69314718055994530942).

M_LN10 (float)

Approximation of ln(10) (2.30258509299404568402).

M_PI_2 (float)

Approximation of π/2 (1.57079632679489661923).

M_PI_4 (float)

Approximation of π/4 (0.78539816339744830962).

M_1_PI (float)

Approximation of 1/π (0.31830988618379067154).

M_2_PI (float)

Approximation of 2/π (0.63661977236758134308).

M_SQRTPI (float)

Approximation of sqrt(π) (1.77245385090551602729).

M_2_SQRTPI (float)

Approximation of 2/sqrt(π) (1.12837916709551257390).

M_SQRT2 (float)

Approximation of sqrt(2) (1.41421356237309504880).

M_SQRT3 (float)

Approximation of sqrt(3) (1.73205080756887729352).

M_SQRT1_2 (float)

Approximation of 1/sqrt(2) (0.70710678118654752440).

M_LNPI (float)

Approximation of ln(π) (1.14472988584940017414).

M_EULER (float)

Approximation of Euler's constant γ (0.57721566490153286061).

IEEE 754 floating point constants

NAN (float)

Not A Number

INF (float)

Infinity

Rounding constants

Note: As of PHP 8.4.0, it is recommended to use the RoundingMode enum instead.

PHP_ROUND_HALF_UP (int)

Rounding half away from zero.

PHP_ROUND_HALF_DOWN (int)

Rounding half toward zero.

PHP_ROUND_HALF_EVEN (int)

Round halves to even numbers

PHP_ROUND_HALF_ODD (int)

Round halves to odd numbers