Common Functions in PHP - Part 2

isset() function

Checks if a variable is set and has a value.

$name = "John";
if (isset($name)) {
    echo "Variable 'name' is set.";
} else {
    echo "Variable 'name' is not set.";
}

empty() function

Checks if a variable is empty or does not exist.

$email = "";
if (empty($email)) {
    echo "Email is not provided.";
} else {
    echo "Email is provided.";
}

exit() or die() function

Stops the execution of the program and displays a message if needed.

$age = 15;
if ($age < 18) {
    echo "You are not old enough to access.";
    exit();
}
echo "Welcome to the website.";

continue control structure

Skips the current iteration of a loop and moves to the next iteration.

for ($i = 1; $i <= 10; $i++) {
    if ($i == 5) {
        continue;
    }
    echo $i . " ";
}
// Output: 1 2 3 4 6 7 8 9 10

break control structure

Terminates a loop or the current execution.

$num = 1;
while (true) {
    echo $num . " ";
    if ($num == 5) {
        break;
    }
    $num++;
}
// Output: 1 2 3 4 5

var_dump() function

Function is used to display detailed information about a variable or value. It allows you to see the data type, value, and size of the variable.

$number = 10;
$string = "Hello";
$array = [1, 2, 3];

var_dump($number); // int(10)
var_dump($string); // string(5) "Hello"
var_dump($array); // array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) }

print() function

Function is used to display a value on the screen. It is similar to echo, but it returns a value of 1 if successful.

$name = "John";

print "Hello, " . $name; // Hello, John

print_r() function

Function is used to display information about a variable or array in a readable format. It is useful when you want to see the structure and values of an array.

$array = [1, 2, 3];

print_r($array);
/* Output:
Array
(
    [0] => 1
    [1] => 2
    [2] => 3
)
*/

Lưu ý: The var_dump, print and print_r functions are often used for debugging purposes, as they do not return a value and only display information on the screen.