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PHP Questionnaire I

What is PHP?

PHP (Hypertext Preprocessor) is a server side scripting language used for creating web applications.

What is the difference between echo and print?

1. print can out only one string where as echo can output one or more strings.

<html>
    <head>
        <title> </title>
    </head>
    <body>
        <?php
		 print("Test 1") ;
		 echo "test2", "test3"	
        ?>
    </body>
</html>

2. echo doesn't return any value, but print returns a boolean value.

<html>
    <head>
        <title> </title>
    </head>
    <body>
        <?php
		 $output = print("Test 1") ;
		 //$output = echo "test2", "test3"	
        ?>
    </body>
</html>

Here second statement(if uncommented) gives compile time error.

What is the difference between preg_split and explode in PHP?

preg_split splits string by the regular expression

<html>
    <head>
        <title> </title>
    </head>
    <body>
        <?php
	$string = "123.456";
	print_r(preg_split("/\./", $string));
        ?>
    </body>
</html>

Output - Array ( [0] => 123 [1] => 456 )

explode splits the string using string literal.

<html>
    <head>
        <title> </title>
    </head>
    <body>
        <?php
	$string = "123.456";
	print_r(explode(".", $string));
        ?>
    </body>
</html>

Output - Array ( [0] => 123 [1] => 456 )

Will comparison of string "10" and integer 10 work in PHP?

Yes.

<html>
    <head>
        <title></title>
    </head>
    <body>
        <?php
	        $numeric_var = 10;
	        $string_var= "10";

	        if($numeric_var == $string_var)
	        {
		        echo "equal";
	        }
	        else
	        {
		        echo "not equal";
	        }
        ?>
    </body>
</html>

Output : equal

What is the difference between == and === in PHP?

Both the operators are used to compare values. In == operator if left hand side value is equal to right hand side value irrespective of data type then the expression using this operator returns true.

<?php

	$numeric_var = 10;
	$string_var= "10";

	if($numeric_var == $string_var)
	{
		echo "equal";
	}
	else
	{
		echo "not equal";
	}
?>

Output: equal

In === operator if left hand side value is equal to right hand side value and data type of left hand side value doesn't match the data type of right hand side value then the expression using this operator returns false.

<?php

	$numeric_var = 10;
	$string_var= "10";

	if($numeric_var === $string_var)
	{
		echo "equal";
	}
	else
	{
		echo "not equal";
	}
?>

Output: not equal

What is the difference between include and require in PHP?

Both statements are used to insert the content of other files. Require produce a fatal error if the file doesn't exists and stop executing the script whereas include will only produce a warning and scripts will execute.

<html>
  <body>
    <div class="leftmenu">
    <?php require 'menu1.php'; ?>
    </div>
    <h1>Welcome to my home page.</h1>
    <p>Some text.</p>
  </body>
</html>

Output: Fatal error: require(): Failed opening required 'menu1.php' (include_path='.;C:\xampp\php\PEAR') in C:\xampp\htdocs\test.php on line 6 and header(Welcome to my home page.) and paragraph(Some text.) doesn't display in the browser.

<html>
  <body>
    <div class="leftmenu">
    <?php include 'menu1.php'; ?>
    </div>
    <h1>Welcome to my home page.</h1>
    <p>Some text.</p>
  </body>
</html>

Output: Warning: include(): Failed opening 'menu1.php' for inclusion (include_path='.;C:\xampp\php\PEAR') in C:\xampp\htdocs\test.php on line 6 and header(Welcome to my home page.) and paragraph(Some text.) will display in the browser.

What is the difference between $message and $$message?

$message is used to store variable data whereas $$message is used to store variable of variable.

Consider an example below

<html>
	<body>
		<?php 
			$message = "you";
			$you= "Me";
			echo $message; 
			echo $$message;
		?>
	</body>
</html>

Here $message contains the value 'you' so the first echo statement displays 'you'. Second statement $$message can be written as

$($message) = $(you) = Me

So second echo statement will display 'Me'.

What does a special set of tags < ?= and ? > do in PHP?

These tags are short cut of echo command

<html>
    <body>
        <?= "Hi"?>
    </body>
</html>

Output: Hi

What is the difference between 23 and 0x23 in PHP?

23 is the decimal notation whereas 0x23 is the hexadecimal notation.

<?php 
	echo 23;
	echo 0x23;
?>

Output: 23 and 35

What is the difference between require and require_once in PHP?

Both the statements are used to include a file. But in require_once, PHP checks if the file is already included or not. If yes then PHP will not include this file again whereas in require we can include a file multiple times.

Posted By -

Karan Gupta

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