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<div id="math.constants" class="appendix">
 <h1 class="title">Vordefinierte Konstanten</h1>

 <p class="simpara">Die aufgelisteten Konstanten
stehen immer zur Verfügung, da sie zum Grundbestand von PHP gehören.</p>
 <dl>
  <strong class="title">Mathematische Konstanten</strong>
  
   <dt id="constant.m-pi">
    <strong><code><a href="math.constants.php#constant.m-pi">M_PI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung der Zahl π (pi).
     (<code class="literal">3.14159265358979323846</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-e">
    <strong><code><a href="math.constants.php#constant.m-e">M_E</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung der Eulersche Zahl <code class="literal">e</code>
     (<code class="literal">2.7182818284590452354</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-log2e">
    <strong><code><a href="math.constants.php#constant.m-log2e">M_LOG2E</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">log<sub class="subscript">2</sub>(e)</code>
     (<code class="literal">1.4426950408889634074</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-log10e">
    <strong><code><a href="math.constants.php#constant.m-log10e">M_LOG10E</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">log<sub class="subscript">10</sub>(e)</code>
     (<code class="literal">0.43429448190325182765</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-ln2">
    <strong><code><a href="math.constants.php#constant.m-ln2">M_LN2</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">ln(2)</code>
     (<code class="literal">0.69314718055994530942</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-ln10">
    <strong><code><a href="math.constants.php#constant.m-ln10">M_LN10</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">ln(10)</code>
     (<code class="literal">2.30258509299404568402</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-pi-2">
    <strong><code><a href="math.constants.php#constant.m-pi-2">M_PI_2</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">π/2</code>
     (<code class="literal">1.57079632679489661923</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-pi-4">
    <strong><code><a href="math.constants.php#constant.m-pi-4">M_PI_4</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">π/4</code>
     (<code class="literal">0.78539816339744830962</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-1-pi">
    <strong><code><a href="math.constants.php#constant.m-1-pi">M_1_PI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">1/π</code>
     (<code class="literal">0.31830988618379067154</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-2-pi">
    <strong><code><a href="math.constants.php#constant.m-2-pi">M_2_PI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">2/π</code>
     (<code class="literal">0.63661977236758134308</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-sqrtpi">
    <strong><code><a href="math.constants.php#constant.m-sqrtpi">M_SQRTPI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">sqrt(π)</code>
     (<code class="literal">1.77245385090551602729</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-2-sqrtpi">
    <strong><code><a href="math.constants.php#constant.m-2-sqrtpi">M_2_SQRTPI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">2/sqrt(π)</code>
     (<code class="literal">1.12837916709551257390</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-sqrt2">
    <strong><code><a href="math.constants.php#constant.m-sqrt2">M_SQRT2</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">sqrt(2)</code>
     (<code class="literal">1.41421356237309504880</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-sqrt3">
    <strong><code><a href="math.constants.php#constant.m-sqrt3">M_SQRT3</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">sqrt(3)</code>
     (<code class="literal">1.73205080756887729352</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-sqrt1-2">
    <strong><code><a href="math.constants.php#constant.m-sqrt1-2">M_SQRT1_2</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">1/sqrt(2)</code>
     (<code class="literal">0.70710678118654752440</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-lnpi">
    <strong><code><a href="math.constants.php#constant.m-lnpi">M_LNPI</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung von <code class="literal">ln(π)</code>
     (<code class="literal">1.14472988584940017414</code>).
    </span>
   </dd>
  
  
   <dt id="constant.m-euler">
    <strong><code><a href="math.constants.php#constant.m-euler">M_EULER</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Näherung der Euler-Konstante γ
     (<code class="literal">0.57721566490153286061</code>).
    </span>
   </dd>
  
 </dl>

 <dl>
  <strong class="title">IEEE-754-Gleitkommakonstanten</strong>
  
   <dt id="constant.nan">
    <strong><code><a href="math.constants.php#constant.nan">NAN</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Not A Number (Keine Zahl)
    </span>
   </dd>
  
  
   <dt id="constant.inf">
    <strong><code><a href="math.constants.php#constant.inf">INF</a></code></strong>
    (<span class="type"><a href="language.types.float.php" class="type float">float</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     Unendlich
    </span>
   </dd>
  
 </dl>

 <dl>
  <strong class="title">Rounding constants</strong>
  <blockquote class="note"><p><strong class="note">Hinweis</strong>: 
   <span class="simpara">
    Seit PHP 8.4.0 wird empfohlen, stattdessen die RoundingMode-Enum zu
    verwenden.
   </span>
  </p></blockquote>
  
   <dt id="constant.php-round-half-up">
    <strong><code><a href="math.constants.php#constant.php-round-half-up">PHP_ROUND_HALF_UP</a></code></strong>
    (<span class="type"><a href="language.types.integer.php" class="type int">int</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     n,5 wird aufgerundet (weg von Null, Kaufmännisches Runden)
    </span>
   </dd>
  
  
   <dt id="constant.php-round-half-down">
    <strong><code><a href="math.constants.php#constant.php-round-half-down">PHP_ROUND_HALF_DOWN</a></code></strong>
    (<span class="type"><a href="language.types.integer.php" class="type int">int</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     n,5 wird abgerundet (hin zu Null)
    </span>
   </dd>
  
  
   <dt id="constant.php-round-half-even">
    <strong><code><a href="math.constants.php#constant.php-round-half-even">PHP_ROUND_HALF_EVEN</a></code></strong>
    (<span class="type"><a href="language.types.integer.php" class="type int">int</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     n,5 wird zur nächsten geraden Zahl gerundet
    </span>
   </dd>
  
  
   <dt id="constant.php-round-half-odd">
    <strong><code><a href="math.constants.php#constant.php-round-half-odd">PHP_ROUND_HALF_ODD</a></code></strong>
    (<span class="type"><a href="language.types.integer.php" class="type int">int</a></span>)
   </dt>
   <dd>
    <span class="simpara">
     n,5 wird zur nächsten ungeraden Zahl gerundet
    </span>
   </dd>
  
 </dl>
</div>
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