name = "No name";
$1x = 20;
$)name = "No name";
$na me = "Hola";
&na-me = "Hello";

$name = "No name";
$x1 = 20;
$_name = "Hello";

$x = 100;
$y = 11;

echo $x + $y . "\n";

echo $x - $y . "\n";

echo $x * $y . "\n";

echo $x / $y . "\n";

echo $x % $y . "\n";

echo $x ** $y . "\n";

<?php 

  // Math functions

    # Function min() finds the lowest value from its arguments, example:
      echo min(21, 78, 20, 47, 89). "\n"; //outputs - 20;
    
    # Function max() finds the highest value from its arguments, example:
      echo max(78, 97, 109, 47, 445). "\n"; //outputs - 445;

    # Function count() counts all elements in the array, example: 
      echo count(67, 89, 76, 54, 9, 90). "\n"; //outputs - 6;

    # Function round() rounds a floating-point number to its nearest integer, example:
      echo(round(9.43)). "\n"; //outputs - 9;
      echo(round(5.5)). "\n"; //outputs - 6;

    # Function floor() rounds the floating-point number down, example:
      echo floor(9.7). "\n"; //outputs - 9;
      echo floor(6.1). "\n"; //outputs - 6;

    # Function ceil() rounds the floating-point number up, example: 
      echo ceil(9.8). "\n"; //outputs - 10;
      echo ceil(7.2). "\n"; //outputs - 8;

    # Function rand() generates a random number, example:
      echo rand(9, 88). "\n"; //outputs some number from 9 to 88;
    
    # Function sqrt() returns the square root of a number, example:
      echo sqrt(81). "\n"; //outputs - 9;

    # Function pow() raises 2 to the power of 3, example:
      echo pow(2, 3). "\n"; //output 8; 

    # Function pi() Returns PI value, example:
      echo pi(). "\n"; //outputs - 3.1415926535898

    # Function abs() returns the positive (absolute) value of a number, example:
      echo abs(-87). "\n"; //outputs - 87;

    # Function decbin() converts decimal number into binary, example: 
      echo decbin(44). "\n"; //outputs - 101100;

?>

primary

alert-primary

<div class="alert alert-primary" role="alert">
  A simple primary alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

secondary

alert-secondary

<div class="alert alert-secondary" role="alert">
  A simple secondary alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

success

alert-success

<div class="alert alert-success" role="alert">
  A simple success alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

danger

alert-danger

<div class="alert alert-danger" role="alert">
  A simple danger alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

warning

alert-warning

<div class="alert alert-warning" role="alert">
  A simple warning alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

info

alert-info

<div class="alert alert-info" role="alert">
  A simple info alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

light

alert-light

<div class="alert alert-light" role="alert">
  A simple light alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

dark

alert-dark

<div class="alert alert-dark" role="alert">
  A simple dark alert with <a href="#" class="alert-link">an example link</a>. Give it a click if you like.
</div>

<nav aria-label="breadcrumb">
  <ol class="breadcrumb">
    <li class="breadcrumb-item"><a href="#">Home</a></li>
    <li class="breadcrumb-item"><a href="#">Library</a></li>
    <li class="breadcrumb-item active" aria-current="page">Data</li>
  </ol>
</nav>

<div class="btn-group" role="group" aria-label="Basic example">
  <button type="button" class="btn btn-secondary">Left</button>
  <button type="button" class="btn btn-secondary">Middle</button>
  <button type="button" class="btn btn-secondary">Right</button>
</div>