As constantes abaixo estão sempre disponíveis como parte do núcleo do PHP.
| Constante | Valor | Descrição | Disponibilidade |
|---|---|---|---|
M_PI |
3.14159265358979323846 | Pi | |
M_E |
2.7182818284590452354 | e - número neperiano | |
M_LOG2E |
1.4426950408889634074 | logaritmo de e na base 2 | |
M_LOG10E |
0.43429448190325182765 | logaritmo de e na base 10 | |
M_LN2 |
0.69314718055994530942 | logaritmo neperiano de 2 | |
M_LN10 |
2.30258509299404568402 | logaritmo neperiano de 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 | raiz(pi) | |
M_2_SQRTPI |
1.12837916709551257390 | 2/raiz(pi) | |
M_SQRT2 |
1.41421356237309504880 | raiz(2) | |
M_SQRT3 |
1.73205080756887729352 | raiz(3) | |
M_SQRT1_2 |
0.70710678118654752440 | 1/raiz(2) | |
M_LNPI |
1.14472988584940017414 | logaritmo neperiano de pi | |
M_EULER |
0.57721566490153286061 | Constante de Euler | |
PHP_ROUND_HALF_UP |
1 | Arredonda 0.5 para cima | |
PHP_ROUND_HALF_DOWN |
2 | Arredonte 0.5 para baixo | |
PHP_ROUND_HALF_EVEN |
3 | Arredonda 0.5 para números pares | |
PHP_ROUND_HALF_ODD |
4 | Arredonda 0.5 para números ímpares | |
NAN |
NAN (como um float) | Not A Number - um não-número | |
INF |
INF (como um float) | Infinito |
I just learnt of INF today and found out that it can be used in comparisons:
echo 5000 < INF ? 'yes' : 'no'; // outputs 'yes'
echo INF < INF ? 'yes' : 'no'; // outputs 'no'
echo INF <= INF ? 'yes' : 'no'; // outputs 'yes'
echo INF == INF ? 'yes' : 'no'; // outputs 'yes'
You can also take its negative:
echo -INF < -5000 ? 'yes' : 'no'; // outputs 'yes'
Division by INF is allowed:
echo 1/INF; // outputs '0'There are also the predefined PHP_INT_MAX and PHP_INT_SIZE constants, that describe the range of possible integer values.Although INF can be used for comparison against normal numbers and as a directed number, and behaves as reciprocal of zero, it is not like limit INF tends to infinity. These operations do not work:
<?php
var_dump(INF / INF); // float(NAN)
var_dump(INF - INF); // float(NAN)
?>
However, it works with arc-tangent:
<?php
var_dump(atan(INF) / M_PI); // float(0.5)
var_dump(atan2(INF, INF) / M_PI); // float(0.25)
var_dump(atan2(1, INF) / M_PI); // float(0)
?>From PHP 7.2.0, the PHP_FLOAT_* constants are provided to describe the properties of floating point numbers that can be stored; PHP_FLOAT_MAX, for example, is analogous to PHP_INT_MAX and represents the largest possible floating-point number.