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Valeri Tandilashvili's Personal Professional Blog
Results: 1024
empty vs isset
Difference between 
empty
and 
isset
$var = 0;

// Evaluates to true because $var is empty
if (empty($var)) {
    echo '$var is either 0, empty, or not set at all';
}

// Evaluates as true because $var is set
if (isset($var)) {
    echo '$var is set even though it is empty';
}
The following values are considered to be false: 
""
(an empty string) 
0
(0 as an integer) 
0.0
(0 as a float) 
"0"
(0 as a string) 
NULL
FALSE
array()
(an empty array)
.btn-block
we can create block level buttons - those that span the full width of a parent by adding 
.btn-block
<button type="button" class="btn btn-primary btn-lg btn-block">Block level button</button>
<button type="button" class="btn btn-secondary btn-lg btn-block">Block level button</button>
composer remove vendor/package vendor/package2
Removes several packages at the same time
composer remove vendor/package vendor/package2
Calendar CODE 

// Example usage:
$year = 2023;
$month = 1; // May

function generateMonthArray($year, $month) {
    $numDays = cal_days_in_month(CAL_GREGORIAN, $month, $year);
    $firstDay = date("N", strtotime("$year-$month-01")); // 1 = Monday, 7 = Sunday

    $weekdays = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'];

    $monthArray = array_fill_keys($weekdays, []);

    for ($day = 1; $day <= $numDays; $day++) {
        $weekday = ($firstDay + $day - 2) % 7; // Adjust to start from Monday
        $monthArray[$weekdays[$weekday]][] = $day;
    }
    
    foreach ($monthArray as &$weekDays) {
    	if ($weekDays[0]!=1) {
    		array_unshift($weekDays, '');
    	} else {
    		break;
    	}
    }

    return $monthArray;
}

$result = generateMonthArray($year, $month);

// Print the result
foreach ($result as $weekday => $days) {
    echo $weekday . "\t" . implode("\t", $days) . "\n";
}
npm run scripts
We can run scripts that are listed in 
scripts
key, inside 
package.json
file. If the content is the following
"scripts": {
    "start": "node app.js",
    "server": "live-server"
}
Then we can run 
npm run start
and npm will run 
node app.js
We can also run 
npm run server
and it will run 
live-server
Function hoisting in PHP CODE
Functions don't need to be defined before they are called. In this example, function 
printMe()
is defined after it's called but it works without errors
echo printMe();

function printMe() {
    return 'Print some text';
}
Exception is 
conditional function
. In this example function 
foo()
will not be defined until the 
if ($makefoo)
conditional statement gets executed
$makefoo = true;

/* We can't call foo() from here 
   since it doesn't exist yet,
   but we can call bar() */
// foo();

bar();

if ($makefoo) {
  function foo()
  {
    echo "I don't exist until program execution reaches me.\n";
  }
}

/* Now we can safely call foo()
   since $makefoo evaluated to true */

if ($makefoo) foo();

function bar() 
{
  echo "I exist immediately upon program start.\n";
}
Functions within functions. Function 
bar()
will not be defined until the function 
foo()
is executed
function foo() 
{
  function bar() 
  {
    echo "I don't exist until foo() is called.\n";
  }
}

/* We can't call bar() yet
   since it doesn't exist. */
// bar();


foo();

/* Now we can call bar(),
   foo()'s processing has
   made it accessible. */

bar();
Note: All functions in PHP have the global scope - they can be called outside a function even if they were defined inside and vice versa
__call 
class Foo {
    
    public function __call($function, $arguments)
    {
        return "$function has been called with arguments: " . implode(', ', $arguments); 
    }
    
    // public function fireFunction($one, $two, $three) {
    //     return "pre-defined method";
    // }
}
$foo = new Foo();
echo $foo->fireFunction(5, 47, "third argument");
__call
is invoked when the method is inaccessible (when it's not public or does not exist at all)
store and read any property using __get and __set 
__get
and 
__set
magic methods allows us to get and set any variable without having individual getter and setter methods:
class Foo {
    protected $properties = array();

    public function __get( $key )
    {
        if(array_key_exists($key, $this->properties)){
            return $this->properties[$key];
        }
        return $this->properties[ $key ];
    }
    public function __set( $key, $value )
    {
        $this->properties[ $key ] = $value;
    }
}
$foo = new Foo();
$foo->name = 'David';

echo $foo->name;
In this example, we can set any variable, even if it does not exist. Every variable will be addd to 
properties
array
VAR uses function scope, LET uses block scope CODE
Variable 
variableVAR
is visible outside the 
if
statement because it uses function scope instead of block scope
function callMePlease() {
  if (1 == 1) {
    let variableLET = 'LET'
    var variableVAR = 'VAR'
  }
  document.write('My ' + variableVAR + '</br>')
  document.write('My ' + variableLET + '</br>')
}

callMePlease()
Another variable 
variableLET
is not visible outside the block because it uses block scope and the code above will generate the following error:
Uncaught ReferenceError: variableLET is not defined
changing attributes: href, text CODE
Changing the 
href
, 
text
of a link JS
//calling the function in window.onload to make sure the HTML is loaded
window.onload = function() {
    var el = document.getElementsByTagName('a');
    el[0].href= 'http://www.sololearn.com';
};
HTML
<a href="http://www.example.com">Some link</a>
<br />
<a href="https://google.com">Google.com</a>
Results: 1024