Predefined Constants
The constants below are always available as part of the PHP core.
Math constants
| Constant |
Value |
Description |
| M_PI |
3.14159265358979323846 |
Pi |
| M_E |
2.7182818284590452354 |
e |
| M_LOG2E |
1.4426950408889634074 |
log_2 e |
| M_LOG10E |
0.43429448190325182765 |
log_10 e |
| M_LN2 |
0.69314718055994530942 |
log_e 2 |
| M_LN10 |
2.30258509299404568402 |
log_e 10 |
| M_PI_2 |
1.57079632679489661923 |
pi/2 |
| M_PI_4 |
0.78539816339744830962 |
pi/4 |
| M_1_PI |
0.31830988618379067154 |
1/pi |
| M_2_PI |
0.63661977236758134308 |
2/pi |
| M_SQRTPI |
1.77245385090551602729 |
sqrt(pi) [5.2.0] |
| M_2_SQRTPI |
1.12837916709551257390 |
2/sqrt(pi) |
| M_SQRT2 |
1.41421356237309504880 |
sqrt(2) |
| M_SQRT3 |
1.73205080756887729352 |
sqrt(3) [5.2.0] |
| M_SQRT1_2 |
0.70710678118654752440 |
1/sqrt(2) |
| M_LNPI |
1.14472988584940017414 |
log_e(pi) [5.2.0] |
| M_EULER |
0.57721566490153286061 |
Euler constant [5.2.0] |
Only M_PI is available in PHP versions up to and including PHP 4.0.0.
All other constants are available starting with PHP 4.0.0. Constants
labeled [5.2.0] were added in PHP 5.2.0.
