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PHP Keywords

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Release： 2024-08-29 12:33:36
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Keywords are the words hold some meaning. In regular use of PHP language, these words cannot be used as a constant, a variable name, a method name, a class name, etc. These keywords when used are automatically understood by PHP. These PHP keywords, when used with variable names, can be confused with the actual keywords. Therefore, these keywords should not be used as variable names.

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List of all PHP keywords

Following is a list:

PHP Keywords

Keyword: abstract

Code:

<?php
//example to demonstrate abstract keyword
abstract class Program {
abstract protected function MethodOne();
public function display() {
echo '<br>'.$this->MethodOne();
}
}
class ProgramOne extends Program {
protected function MethodOne() {
echo '<br>'.'In MethodOne';
}
}
$objOne = new ProgramOne;
$objOne->display();
?>,
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Output:

PHP Keywords

Keyword: and

Code :

<?php
//example to demonstrate and keyword
$a = 10;
$b = 11;
if($a ==10  and  $b == 11) {
echo 'Result :  True';
}
else
{
echo 'Result : False';
}
?>
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Output: 

PHP Keywords

Keyword: array()

Code:

<?php
//example to demonstrate array keyword
$directions  = array("e" => "east", "w" => "west", "n" => "north", "s" => "south");
print_r($directions);
?>
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Output:

PHP Keywords

Keyword: as

Code:

<?php
//example to demonstrate array keyword
$directions  = array("e" => "east", "w" => "west", "n" => "north", "s" => "south");
foreach($directions as $key=>$value) {
echo '<br>'. $key. '=>'.$value;
}
?>
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Output:

PHP Keywords

Keyword: break

Code :

<?php
//use of break keyword without optional argument
$arr = array("water", "sky", "try", "sand");
foreach($arr as $key=>$value) {
if($value  == 'try') {
break ;          // can use break 1 also
}
echo '<br>'.$value;
}
?>
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Output:

PHP Keywords

Keyword: case

Code:

<?php
//example to demonstrate case keyword
$i = 1;
while($i<5) {
switch($i) {
case 1:
echo "<br>"."One";
break;
case 2:
echo "<br>"."Two";
break;
case 3:
echo "<br>"."Three";
break;
default:
echo "<br>"."Default";
}
$i++;
}
?>
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Output: 

PHP Keywords

Keyword:  catch

Code:

<?php
//example to demonstrate catch keyword
function Operation()
{
try {
$num1 = 10;
$num2 = 0;
if($num1 / $num2) {
throw new Exception('Divide By Zero');
}
} catch (Exception $e) {
die($e->getMessage());
}
}
Operation();
?>
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Output:

PHP Keywords

Keyword: class

Code:

<?php
//example to demonstrate class keyword
class ClassOne{
var $str = 'Hello World';
public function displayMethod() {
echo $this->str;
}
}
$obj = new ClassOne;
$obj->displayMethod();
?>
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Output:

PHP Keywords

Keyword: const

the const keyword is used to define the name with a value using assignment operator like below

const AGE= 29;

There is no $ sign at the beginning of a constant name like a normal variable has.

Keyword: default

Code:

<?php
// example to demonstrate default keyword
$fruits = 'Cherries';
switch ($fruits) {
case 'Apple':
echo "Apple";
break;
case 'Banana':
echo "Banana";
break;
case 'Papaya':
echo "Papaya";
break;
default:
echo "Fruit is not Apple, Banana or Papaya ";
break;
}
?>
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Output :

PHP Keywords

Keyword: do

Code:

<?php
// example to demonstrate do keyword
$x = 2;
do {
if($x > 2)
{
echo 'x is greater than 2';
}
else{
echo 'x is less than 2';
}
} while ($x < 2);
?>
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Output:

PHP Keywords

Keyword: die();

Code :

<?php
//example to demonstrate die keyword
$conn = mysqli_connect('localhost','root','','dbname');
if(!$conn) {
die("Unable to connect ");
}
?>
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Output:

PHP Keywords

Keyword: echo

Code:

<?php
// example to demonstrate echo keyword
echo 'Hello! ';
$name = 'John Doe';
echo 'My name is '. $name;
?>
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Output:

PHP Keywords

Keyword: else

Code:

<?php
// example to demonstrate else keyword
$a = 10;
if ($a > 5) {
echo "a is greater than 10";
} else {
echo "a is not greater than 10";
}
?>
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Output:

PHP Keywords

Keyword: elseif

Code:

<?php
// example to demonstrate elseif keyword
$a = 10;
if ($a > 10) {
echo "a is greater than 10";
} elseif ($a == 10) {
echo "a is equal to 10";
} else {
echo "a is smaller than 10";
}
?>
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Output :

PHP Keywords

Keyword: empty

Code:

<?php
// example to demonstrate empty keyword
$str = 'Hello World!';
if(empty($str)) {
echo 'Variable is empty';
} else {
echo $str;
}
?>
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Output:

PHP Keywords

Keyword: endfor

Code:

<?php
// example to demonstrate endfor keyword
for($i=0;$i<5;$i++) :
echo "<br/>".$i;
endfor;
?>
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Output:

PHP Keywords

Keyword: endif

Code :

<?php
// example to demonstrate endif keyword
if ($a > 10):
echo "a is greater than 10";
elseif ($a >10) :
echo "a is equal to 10";
else:
echo "a is not equal to 10";
endif;
?>
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Output:

PHP Keywords

Keyword: endforeach

 Code: 

<?php
// example to demonstrate endforeach keyword
$arr = array(1,2,3,4,5,6,7,8,9,10);
foreach ($arr as $key=>$value):
echo '<br>'.$value;
endforeach;
?>
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Output:

PHP Keywords

Keyword: endswitch

Code:

<?php
// example to demonstrate endswitch keyword
$fruits = 'Cherries';
switch ($fruits):
case 'Apple':
echo "Apple";
break;
case 'Banana':
echo "Banana";
break;
case 'Papaya':
echo "Papaya";
break;
default:
echo "Fruit is not Apple, Banana or Papaya ";
break;
endswitch;
?>
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Output:

PHP Keywords

Keyword: endwhile

Code:

<?php
// example to demonstrate endwhile keyword
$i = 0;
while($i<5):
echo "<br>".$i;
$i++;
endwhile;
?>
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Output:

PHP Keywords

Keyword: eval()

Code:

<?php
//example to demonstrate eval keyword
$string1 = 'World';
$string2 = 'John Doe';
$string = 'Hello $string1 .  My name is $string2';
echo "<br>".$string;
eval("\$string = \"$string\";");
echo "<br>".$string;
?>
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Output:

PHP Keywords

Keyword: exit()

This keyword when encountered in a script, terminates the execution of the script.

Keyword: extends()

Code:

<?php
//example to demonstrate extends keyword
class ParentClass {
var $string = 'PHP';
public function display() {
echo $this->string;
}
}
class ExtendClass extends ParentClass {
public function display() {
echo 'Hello World!';
}
}
$obj1 = new ExtendClass;
$obj1->display();
?>
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Output:

PHP Keywords

Keyword: final

Code:

<?php
//example to demonstrate final keyword
class ParentClass {
var $string = 'PHP';
final public function display() {
echo $this->string;
}
}
class ExtendClass extends ParentClass {
public function display() {
echo 'Hello World!';
}
}
$obj1 = new ExtendClass;
$obj1->display();
?>
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Output :

PHP Keywords

Keyword: catch

Code:

<?php
//example to demonstrate catch keyword
try {
$num1 = 10;
$num2 = 0;
if($num1 / $num2) {
throw new Exception('Divide By Zero');
}
} catch (Exception $e) {
echo '<br>'.$e->getMessage();
}
?>
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Output:

PHP Keywords

Keyword: for

Code:

<?php
// example to demonstrate for keyword
for($i=0; $i<10; $i++) {
if($i == 5) {
break;
}
echo '<br>'.$i;
}
?>
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Output :

PHP Keywords

Keyword: foreach

Code:

<?php
// example to demonstrate foreach keyword
$array = array(10,20,30,40,50);
foreach($array as $value) {
echo '<br>'.$value/10;
}
?>
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Output:

PHP Keywords

Keyword: function()

Code:

<?php
function calSum($a , $b) {
$c = $a + $b;
return $c;
}
$result = calSum(10 , 20);
echo '<br> The sum  :  '.$result;
?>
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Output:

PHP Keywords

Keyword 34: global

Code:

<?php
//example to demonstrate global keyword
$a = 10;
$b = 20;
function fun() {
global $a;
global $b;
$result = $a + $b;
return $result;
}
$f = fun();
echo 'The result is '.$f;
?>
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Output:

PHP Keywords

Keyword: if

Code:

<?php
// example to demonstrate if keyword
$sum = 10;
if($sum == 10) {
echo 'Sum is 10';
} else {
echo 'Sum is not 10';
}
?>
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Output:

PHP Keywords

Keyword: implements

Code:

<?php
//example to demonstrate interface keyword
interface One
{
public function first();
}
class MainClass implements One {
public function first() {
echo 'This is the First function';
}
}
$obj = new MainClass;
echo $obj->first();
?>
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Output :

PHP Keywords

Keyword: include

Code:

file.php

<?php
//example to demonstrate include keyword
$a = 'The Earth';
$b = 'Round';
?>
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index.php

<?php
include 'file.php';
echo $a . ' is '. $b. ' in Shape';
?>
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Keyword  : include_once

Code:

file.php

<?php
//example to demonstrate include_once keyword
$a = 'The Earth';
$b = 'Round';
?>
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index.php

<?php
Include_once 'file.php';
echo $a . ' is '. $b. ' in Shape';
?>
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Output:

PHP Keywords

Keyword: instanceOf

Code:

<?php
//example to demonstrate instanceOf keyword
class MainClass
{
public function MainCLassMethod(){
echo 'Hello World!';
}
}
class ExtendedClass extends MainClass
{
public function ExtendedClassMethod(){
echo 'Have a Nice Day!';
}
}
$obj1 = new ExtendedClass;
var_dump($obj1 instanceOf ExtendedClass);
?>
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Output:

PHP Keywords

Keyword: Interface

Code:

<?php
//example to demonstrate interface keyword
interface One
{
public function one();
}
interface Two
{
public function two();
}
class MainClass implements One, Two {
public function one() {
echo '<br> This is the one function';
}
public function two() {
echo '<br> This is the two function';
}
}
$obj = new MainClass;
echo $obj->one();
echo $obj->two();
?>
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Output:

PHP Keywords

Keyword: isset

Code:

<?php
//example to demonstrate isset keyword
$stringOne = '';
var_dump(isset($stringOne));
$stringTwo = NULL;
var_dump(isset($stringTwo));
?>
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Output :

PHP Keywords

Keyword: list

Code:

<?php
//example to demonstrate list keyword
$names = array('Ram','Mohan','Raghav');
list($person1, $person2, $person3) = $names;
echo "$person1, $person2 and $person3 are friends";
?>
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Output:

PHP Keywords

Keyword: new

Code:

<?php
//example to demonstrate new keyword
class Student
{
public function score($name, $subject, $marks) {
echo "$name scored $marks marks in $subject";
}
}
$obj = new Student;
$obj->score('Sunil','Maths',90);
?>
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Output:

PHP Keywords

Keyword: or

Code:

<?php
//example to demonstrate or keyword
$a = 10;
$b = 11;
if($a ==10  or $b == 12) {
echo 'Result :  True';
}
else
{
echo 'Result : False';
}
?>
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Output :

PHP Keywords

Keyword: print

Code:

<?php
//example to demonstrate print keyword
$str = "PHP Programming";
print($str);
$stringOne = "Shyam, ";
$stringTwo = "How are you?";
print "<br>"."Hello $stringOne $stringTwo";
?>
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Output :

PHP Keywords

Keyword: private

Code:

<?php
//example to demonstrate private keyword
class MainClass
{
private $str = 'Private';
function PrivateMethod()
{
echo 'In '. $this->str. ' Method';
}
}
$obj = new MainClass();
$obj->PrivateMethod(); //Shows Private Method
?>
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Output:

PHP Keywords

Keyword: public

Code:

<?php
//example to demonstrate public keyword
class MainClass
{
public $str = 'Public';
function PublicMethod()
{
echo 'In '. $this->str. ' Method';
}
}
$obj = new MainClass();
$obj->PublicMethod(); //Shows Public Method
?>
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Output:

PHP Keywords

Keyword: protected

Code:

<?php
//example to demonstrate protected keyword
class MainClass
{
protected $str = 'Protected';
function ProtectedMethod()
{
echo 'In '. $this->str. ' Method';
}
}
$obj = new MainClass();
$obj->ProtectedMethod(); //Shows Protected Method
?>
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 Output:

PHP Keywords

Keyword: return

Code:

<?php
//example to demonstrate return keyword
function sum() {
$a = 10;
$b = 20;
$c = $a +$b;
return $c;
}
$result = sum();
echo 'Sum : ' . $result;
?>
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Output:

PHP Keywords

Keyword: switch

Code:

<?php
//example to demonstrate switch keyword
$i= 3;
switch($i) {
case 1:
echo "<br>"."One";
break;
case 2:
echo "<br>"."Two";
break;
case 3:
echo "<br>"."Three";
break;
default:
echo "<br>"."Default";
}
?>
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Output:

PHP Keywords

Keyword: throw

Code:

<?php
//example to demonstrate throw keyword
function division($x, $y) {
try {
if($y == 0) {
throw new Exception('Divide By Zero');
}
}
catch (Exception $e) {
echo '<br>'.$e->getMessage();
}
}
division(10,0);
?>
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Output:

PHP Keywords

Keyword: Try

Code:

<?php
//example to demonstrate try keyword
try{
$arr = array();
$arr_length = count($arr);
if($arr_length == 0) {
throw new Exception('Error : Empty Array!');
}
else {
echo 'Array found';
print_r($arr);
}
}
catch(Exception $e) {
echo '<br>'.$e->getMessage();
}
?>
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Output:

PHP Keywords

Keyword: unset

Code:

<?php
//example to demonstrate unset keyword
echo 'Hello World!'.'<br>';
$a = 10;
echo $a;
unset($a);
// echo $a; //this line when uncommented shows error : Undefined variable,  as the variable is unset
?>
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Output:

PHP Keywords

Keyword: var

Code:

<?php
//example to demonstrate var keyword
class MainClass
{
var $str = 'PHP Programming';
public function displayMsg() {
echo $this->str;
}
}
$obj = new MainClass;
$obj->displayMsg();
?>
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Output:

PHP Keywords

Keyword: while

Code: 

<?php
//example to demonstrate while keyword
$i = 0;
while ($i<10) {
echo '<br>'. $i;
$i++;
}
?>
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 Output:

PHP Keywords

Conclusion

 In this article, you will learn about keywords in PHP with examples. These examples explain the usage of each of the keyword in PHP.

The above is the detailed content of PHP Keywords. For more information, please follow other related articles on the PHP Chinese website!

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