PHP 8.4.0 RC4 available for testing

Costanti predefinite

Le costanti qui elencate sono sempre disponibili in quanto parte del core di PHP.

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

Nota: 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
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User Contributed Notes 4 notes

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39
md2perpe at gmail dot com
9 years ago
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'
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18
Hayley Watson
12 years ago
There are also the predefined PHP_INT_MAX and PHP_INT_SIZE constants, that describe the range of possible integer values.
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6
pemapmodder1970 at gmail dot com
8 years ago
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)
?>
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2
Hayley Watson
7 years ago
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.
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