PHP Tutorial – GreatLearning

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PHP Tutorial – GreatLearning

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December 17, 2020

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PHP is a powerful tool that is used for creating interactive web pages. This server scripting language is a very popular choice for programmers for creating dynamic web pages.

Since PHP is a free tool, it is often seen as a perfect alternative to competitors like Microsoft ASP. In this article, we are going to discuss the most commonly asked PHP interview questions.

PHP Math:

PHP provides number of built-in function which help in performing several operations while dealing with mathematical data. There is no installation required to use these functions. There are number of in-built functions in PHp and some of them are abs(), pi(), deg2rad(), rad2deg(),fmod(), ceil(), floor(), round().

All the in-built functions mentioned above are described below:

1.abs()
pi()
deg2rad()
rad2deg()
fmod()
ceil()
floor()
round()

Let’s discuss them in detail.

1.abs():

This function takes negative value as an input and return an absolute (positive value) as output. Of an integer or a float number.

Syntax:

abs(number);

In this number can be integer or float number.

Example:

<?php

Function absolute($degree)

{

Return(abs($degree));

}

$number=-8.4;

Echo (absolute($number));

Output:

8.4

2.pi():

This function returns the value of pi. The constant named M_PI is identical to PI() function.

Syntax:

Pi();

Example:

<?php

Echo (pi());

Output:

3.14159

3.deg2rad():

This function takes the degree value as an input and return the radian value as an output.

Syntax:

Deg2rad(number);

Example:

<?php

Function deg_radian($degree)

{

Return (deg2rad($degree));

}

$number=180;

Echo (deg_radian($number));

Output:

3.14259

4.rad2deg();

This function takes an input as radian value and converts into a degree value.

Syntax:

Rad2deg(number);

Example:

<?php

Rad2deg(pi()));

Output:

180

5. Fmod():

This function takes the two arguments as an input and returns the floating number remainder of division of arguments.

Syntax:

Fmod(x,y);

Here x is dividend and y is divisor. The remainder r is defined as, x=i*y+r, for some integer r.

Example:

<?php

Function result($x, $y)

{

Return fmod($x, $y);

}

$x=5.7;

$y=1.3;

Echo(result($x, $y));

Output:

0.5;

6.floor();

This function takes the numeric value as an integer and return the next lowest integer value( as float) by rounding down value if necessary.

Syntax:

Floor($number);

Example:

<?php

Echo (floor(0.60).”n”);

Echo (floor(5).”n”);

Echo (floor(-5.9).”n”);

Output:

-6

7.Ceil();

This function takes numeric value as an input and returns the next highest integer value by rounding up the value if necessary.

Syntax:

Ceil($number );

Example:

<?php

Echo(ceil(0.60).”n”);

Echo(ceil(-5.9)):

Output:

-5

8.round();

This function takes the numeric value as an argument and returns the next highest integer value by rounding up the value if necessary.

Syntax:

Round(number, precision, mode);

Number specifies the value to round, precision specifies the number of decimal digits to round( default 0) and mode specifies one of the following constants to specify the mode in which rounding occurs;

PHP_ROUND_HALF_UP: (set to default) it round the number up to precision decimal, when it is half way there.
PHP_ROUND_HALF_DOWN: Round number down to precision decimal places, when it is half way there. Rounds 1.5 to 1 and -1.5 to -1
PHP_ROUND_HALF_EVEN : Round number to precision decimal places towards the next even value.
PHP_ROUND_HALF_ODD : Round number to precision decimal places towards the next odd value.

Example:

<?php

echo(round(1.95583, 2).”n”);

echo(round(1241757, -3).”n”);

echo(round(9.5, 0, PHP_ROUND_HALF_UP).”n”);

echo(round(9.5, 0, PHP_ROUND_HALF_DOWN).”n”);

echo(round(9.5, 0, PHP_ROUND_HALF_EVEN).”n”);

echo round(9.5, 0, PHP_ROUND_HALF_ODD);

PHP constants:

Variables are useful when you need to store information that can be changed as program runs. However, there may be certain situations in which you are not required to modify or change the values of variables in the program. This is accomplished using constants. Thus constant variables are those variables whose value cannot be changed during the execution of program or after once you have declared the variable. The variables with constant value will be having the same value as long as program runs.

Constants in php are defined using PHP define() function which accepts two arguments; the name of the constant and it’s value. Once defined , the value can be accessed at any time just by referring it’s name.

Example:

<?php

Define(“Site_URL”, “www.xyz.com”);

Echo “Thank you for visiting-“ .Site_URL;

Output:

Thank you for Visiting- www.xyz.com

Naming Conventions for PHP Constants:

Names of constants should follow the same rules as that of variables name in PHP. Thus valid constants should start with letter or underscore, followed by any number of letter, numbers or underscores with one exception that “$ prefix is not required for constants names”.

PHP constants can also be defined using Const() keyword:

Const() keyword is used to define constants in PHP but only scalar constants such as integer. Float, Boolean and strings.

<?php

Const OMG=”Oh! My God”;

Echo OMG;

?>
Output:

Oh! My God

PHP OPERATORS:

Operators are used to perform operations on some values. We can also describe operators as something that take values, perform some operations on them and then gives a result.

For example, “1+ 2= 3” in this expression”+” is an operators. It takes two values 1 and 2 , performs addition operation on them to give 3.

The addition (+) is the operator that tells PHP to add two variables or values, whereas greater than (>) symbol is the operator that tells the PHP to compare two values.

Just like other programming languages Php also supports various types of operations like the Arithmetic operation( addition, subtraction, multiplication, divison, etc.), logical operations( AND, OR. Etc.). Increment and Decrement operations etc.

Operators are used to perform operations on PHP variables and simple values.

In PHP there are total 7 types of operators, they are:

Arithmetic Operators
Assignment Operators
Comparison Operators
Increment/Decrement Operators
Logical Operators
String Operators
Array Operators

There are a few additional operators as well like, Type operator, Bitwise operator, Execution operators etc.

Based on how these operators are used, they are categorised into 3 categories:

Unary Operators: Works on a single operand(variable or value).
Binary Operators: Works on two operands(variables or values).
Ternary Operators: Works on three operands.

PHP Arithmetic Operators

The arithmetic operators are used to perform common arithmetic operations such as addition, subtraction, multiplication, division, etc.

Below is the complete list of PHP arithmetic operators:

Operator	Description	Example	Result
+	Addition	$x+$Y	Sum of $x and $Y
–	Subtraction	$x-$y	Subtraction of $x and $Y
*	Multiplication	$x*$y	Multiplication of $x and $Y
/	Division	$x/$y	Division of $x and $Y
%	Modulus	$x%$y	Modulus of $x and $Y

The example of all the arithmetic operators in PHP program is as follows:

<?php

$x =10;

$y=4;

Echo($x +$y); //outputs:14

Echo($x -$y); //outputs:6

Echo($x *$y); //outputs:40

Echo($x /$y); //outputs:2.5

Echo($x %$y); //outputs:2

PHP Assignment Operators:

The PHP assignment operators are used to assign values to variables.

Operator	Description	Example	Is same as
=	Assign	$x=$y	$x=$y
+=	Add and assign	$x+=$y	$x= $x + $y
-=	Subtract and assign	$x-=$y	$x= $x – $y
*=	Multiply and assign	$x*=$y	$x= $x * $y
/=	Divide and assign quotient	$x/=$y	$x= $x /$y
%=	Divide and assign modulus	$x%=$y	$x= $x % $y

The example of all the assignment operators in PHP program is as follows:

<?php

$x=10;

echo $x; // output:10

$x=20;

$x +=30;

echo $x; // output: 50

$x= 50;

$x-=20;

Echo $x: //output:30

$x= 5;

$x*=25;

Echo $x: //output:125

$x= 50;

$x/=10;

Echo $x: //output:5

$x= 100;

$x%=15;

Echo $x: //output:10

PHP comparison operators

The Comparison operators in PHP are used to compare two values in Boolean Fashion.

Operators	Name	Example	Result
==	Equal	$x = = $y	True if $x is equal to $y
===	Identical	$x= = = $y	True if $x is equal to $y, and they are of same type
!=	Not equal	4x!= $y	True if $x is not equal to $y
< >	Not eual	$x < >$y	True if $x is not equal to $y
!= =	Not identical	$x! = = $y	True if $x is not equal to $y, or they are not of same type
<	Less than	$x < $y	True if $x is less than $y
>	Greater than	$x > $y	True if $x is greater than $y
>=	Greater than or equal to	$x>=$y	True if $x is greayer than or equal to $y
<=	Less than or equals to	$x< =$y	True if $x is lessthan or equal to $y

The example of all the comparison operators in PHP program is as follows:

<?php

$x=25;

$y=35;

$z=”25”;

Var_dump( $x = =$z); // output: boolean true

Var_dump( $x = = =$z); // output: boolean false

Var_dump( $x ! =$y); // output: boolean true

Var_dump( $x <$y); // output: boolean true

Var_dump( $x >$y); // output: boolean false

Var_dump( $x < =$y); // output: boolean true

Var_dump( $x > =$y); // output: boolean false

PHP incrementing and decrementing operators:

The increment and decrement operator in PHP are used to increment or decrement a variable’s value.

Operators	Name	Effect
++$x	Pre-increment	Increments $x by one, then returns $x
$x++	Post-increment	Returns $x, then increment $x by one
–$x	Pre-decrement	Decrements $x by one, then returns $x
$x–	Post-decrement	Returns $x, then decrement $x by one

The example of all the increment and decrement operators in PHP program is as follows:

<?php

$x =10;

echo ++$x; // outputs:11

echo $x; // outputs: 11

$x =10;

echo $x++; // outputs:10

echo $x; // outputs: 11

$x =10;

echo –$x; // outputs:9

echo $x; // outputs: 9

$x =10;

echo $x–; // outputs:10

echo $x; // outputs: 9

Php Logical Operators

The logical operators are typically used to combine conditional sattements.

Operators	name	Example	Result
and	And	$x and $y	True if both $x and $y are true
or	Or	$x or $y	True if either $x or $y is true
xor	Xor	$x xor $y	True if either $x and $y is true, but not both
&&	And	$x && $y	True if both $x and $y are true
\|\|	Or	$x \|\| $y	True if either $x or $y is true
!	Not	! $x	True if both $x is not true

The example of all the logical operators in PHP program is as follows:

<?php

$year =2014

// Leap years are divisible by 400 or by 4 but not by 100

If(($ year % 400= =0) || (($year %100 != 0) && ($ year 5 4 = =0)))

{

Echo “ $year is a leap year.”;

}

Else

{

Echo”$year is not a leap year.”;

}

PHP string Operators:

There are two operators that are specifically designed for string characters.

Operators	Description	Example	Result
.	Concatenation	$str1. $str2	Concatenation of $str1 and $str2
.=	Concatenation assignment	$str1.= $str2	Appends the $str2 to $str1

The example of all the string operators in PHP program is as follows:

<?php

$x =”Hello”;

$y=”World!”;

Echo $x. $y;// outputs: Hello World!

$x.=$y;

Echo $x; // outputs: Hello world!

PHP Array Operators:

The array operators are used to compare arrays.

Operators	Name	Example	Result
+	Union	$x + $y	Union of $x and $y
= =	Equality	$x = = $y	True if $x and $y have the same key/ value pair
= = =	Identity	$x = = =$y	True if $x and $y have the same key/ value pair in the same order and of the same types
!=	Inequality	$x!=$y	True if $x is not equal to $y
< >	Inequality	$x< >$y	True if $x is not equal to $y
!= = =	Non-identity	$x!= =$y	True if $x is not identical to $y

The example of all the array operators in PHP program is as follows:

<?php

$x= array(“a”=>”red”, “b”=>”Green”,”c”=>”Blue”);

$y= aaray(“u”=>”Yellow”,”v”=>”Orange”,”w”=>”Pink”);

$z=$x+$y;// union of $x and $y

Var_dump($z);

Var_dump($x= = $y); // outputs: Boolean false

Var_dump($x= = = $y); // outputs: Boolean false

Var_dump($x! = $y); // outputs: Boolean true

Var_dump($x< >$y); // outputs: Boolean true

Var_dump($x!= = $y); // outputs: Boolean true

PHP spaceship operators

PHP 7 introduces a new spaceship operator(< =>) which can be used for comparing two expressions. It is also known as combined comparison operator.

The spaceship operator returns 0 if both operands are equal, 1 if the left operand is greater and -1 if the right operand is greater.

It basically provides three-way comparison as shown in the following table;

Operators	< => equivalent
$x < $y	($x < = >$y) = = = -1
$x <=$y	($x < = >$y) = = = -1 \|\| ($x < = >$y) = = = 0
$x ==$y	($x < = >$y) = = = 0
$x!=$y	($x < = >$y)! = = 0
$x>=$y	($x < = >$y) = = = 1\|\|($x < = >$y) = = = 0
$x>$y	($x < = >$y) = = = 1

The example of all the spaceship operators in PHP program is as follows:

<?php

// comparing integers

Echo 1< = >1; // outputs: 0

Echo 1< = >2; // outputs:-1

Echo 2< = >1; // outputs: 1

//comparing floats

Echo 1.5< = >1.5; // outputs: 0

Echo 1.5< = >2.5; // outputs: -1

Echo 2.5< = >1.5; // outputs: 1

//comparing strings

Echo “x”< = >”x”; // outputs: 0

Echo “x”< = >”y”; // outputs: -1

Echo “y”< = >”x”; // outputs: 1

The Ternary operator

The Ternary operator provides a shorthand way of writing the If…..else statements. It is represented by question (?) mark symbol and it takes three operands; a condition to check, a result for true, and a result for false.

Let us understand the ternary operator by considering the following example:

<?php

If($age < 18)

{

Echo”child”:// Display child if age is less than 18

}

Else

{

Echo “Adult”:// Display Adult if age is greater than 18

}

Using the ternary operator the same code could be written in more compact way as follows:

<?php

Echo ($age <18) ? ‘Child’: “Adult’;

The ternary operator in the example above selects the value on the left of colon if the condition evaluates to true and the value on right of colon if the condition evaluates to false.

The Null Coalescing operator:

PHP 7 introduces a new Null Coalescing Operator (??) which you can use as a shorthand where you need to use ternary operator in conjunction with isset() function.

To understand this in better way let us consider the following lines of code.

It fetches the value of $_Get[‘name’]. if it does not exist or Null, it returns ‘ anonymous’.

<?php

$name= isset($_Get[‘name’])? $-Get[‘name’]: ‘anonymous’;

Using the Null Coalescing operator the above code could be written as:

<?php

$name=$_Get [‘name;] ?? ‘anonymous’;

PHP LOOPS:

Loops are used to execute the same block of code again and again. As long as certain condition is met. The basic idea behind the loop is to automate the repetitive tasks within the program to save the time and effort.

PHP supports four different types of loops:

While loop :

It loops through a block of code as long as the condition that is specified evaluates to true.

Do…while loop:

In this loop block of code is executed once and then condition is evaluated. If the condition evaluates to true then the statement is repeated as long as specified condition evaluated to true.

For loop:

It loops through a block of code until the counter reaches a specified number.

Foreach loop:

It loops through a block of code for each element in an array. This loops works specifically with arrays.

PHP while loop:

The While statement will loop through a block of code as long as the condition specified in while statement evaluates to true.

Syntax for while loop is as:

While(Condition to be evaluated)

{

//code to be executed

}

The example below defines a loop which starts with $i=1. The loop will continue to run as long as $i is less than or equal to 3. The $i will increase by 1 each time the loop runs:

<?php

$i=1;

While($i<=3)

{

$I++;

Echo” The number is “. $i . “ ”;

}

PHP do…….while loop:

The do-while loop is a variant of while loop, which evaluates the condition at the end of each loop iteration. With the do-while loop the block of code is executed only once, and then the condition specifies is evaluated, if the condition is true then the statement is repeated as many times as the specified condition evaluates to true.

The do-while statement is an exit-controlled statement as test condition is checked at the end of do-while loop and therefore body is executed unconditionally for the first time.

The Syntax for do-while loop is:

{

//code to be executed

}

While(condition to be evaluated);

<?php

$i=1;

{

$i++;

Echo” The number is” .$i. “ ”;

}

While($i<=3);

PHP For Loop:

The for loop is another form of looping statement which is the most versatile, convenient and popular of three loop structures. It is used in those cases where a programmer known in advance that for how many number of times a statement or block of code will be executed.

The Syntax for For lop is as follows:

<?php

For (initialize; condition; increment)

{

//code to be executed

}

In the above code “initialize” usually an integer ; it is used to set the counter’s initial value.

“Condition” the condition that is evaluated for each php execution. If it evaluates to true then execution of for…loop is terminated and if it evaluates to false, the execution of for…loop continues.

“Increment” is used to increment the initial value of counter integer.

Example:

<?php

For($i=0; $i<10; $i++)

{

$product =10 * $i;

Echo “ The product of 10 *$i is $product ”;

}

Output:

The product of 10 * 0 is 0

The product of 10 * 1 is 10

The product of 10 * 2 is 20

The product of 10 * 3 is 30

The product of 10 * 4 is 40

The product of 10 * 5 is 50

The product of 10 * 6 is 60

The product of 10 * 7 is 70

The product of 10 * 8 is 80

The product of 10 * 9 is 90

PHP For Each Loop:

The php for each loop is used to iterate through array values.

It has the following syntax:

<?php

Foreach($array_variable as $array_variable)

{

//block of code to be executed

}

“$array_data” is the array variable to be looped through

:$array_value” is the temporary variable that holds the current array item values.

“block of code..” is the piece of code that operates on array values.

Example:

<?php

$animal_list= array(“Lion”,”Wolf”,”Dog”,”Leopard”,”Tiger”);

Foreach($animal_list as $array_values)

{

Echo $array_values, “ ”;

}

Output:

Lion

Wolf

Dog

Leopard

Tiger

Summary:

The while..loop is used to execute a block of code as long as set condition is made to be false

The do..while loop is used to execute the block of code at least once then the rest of execution is dependent on the evaluation of set condition.

The for loop is used to execute a block of code for specified number of times

The foreach loop is used to loop through arrays.

Php Conditional statements:

These are also refered as Decision control Statements. These statements alter the normal sequential execution of statements of program depending upon the test condition to be carried out at a particular point in the program.The decision to betaken regarding where the control shoukd transfer depends upon the outcome of test condition.

You can create test condition in the form of expression that evaluates to either true or false then you can perform certain actions based on the result.

There are several statements in PHP that you can use to make decisions.

The if statement

The if..else statement

The if…elseif..else statement

The switch ..case statement

The if statement:

It is used to execute a statement or a statement block if the condition is true.

The syntax for if statement is:

If(Condition)

{

Statement(s);

}

The keyword IF tells the interpreter that a decision control statement is to executed. The condition following the if keyword includes any relational or logical expression which is always enclosed within the parenthesis. If the condition is TRUE then the statements in the block are executed. If the condition is false then block of statements is ignored and the control transfers to next statement following the If construct.

The following example will give the output “ Have a nice weekend” if the current day is Friday:

<?php

$d = date(“D”);

If($d = = “Fri”)

{

Echo “have a nice weekend”;

}

The if…else statement:

In case of if statement , the block of statements are executed inly if the condition is true. But if the condition is false nothing is don and the control is transferred to next statement following If construct. However, if specific statements are to be executed in both the cases either condition is true or fasle then if-else statement is used.

The if-else statement allows the programmer to execute a block of statement following the if keyword when condition is true and execute a different statement block following else keyword when condition evaluates to false.

The general form of if-else statement is:

If(condition)

{

Statements to be executed

}

Else

{

Statements to be executed

}

The following example will give output “ Have a nice weekend “ if the current day is Friday, otherwise it will give output as “ have a nice day”:

<?php

$d = date(“D”);

If($d= = “Fri”)

{

Echo” have a nice weekend”;

}

Else

{

Echo “have a nice day”;

}

The if…elseif…else statement

The if…elseif…else statement is the special statement that is used to combine multiple if..else statement.

The general form is as follows:

If(condition 1)

{

//code to be executed if condition 1 is true

}

Elseif (condition 2)

{

//code to be executed if condition 1 is false and condition 2 is true}

Else

{

//code to be executed if both condition 1 and condition 2 are false

}

The following example will give output “Have a nice weekend” if current day is Friday, and “ Have a nice Sunday”, if the current day is Sunday, otherwise it will give output “ Have a nice day”

<?php

$d = date(“D”);

If($d= = “fri”)

{

Echo “Have a nice weekend”;

}

Elseif ($d ==”sun”)

{

Echo “ Have a nice Sunday”;

}

Else

{

Echo “ Have a nice day”;

}

PHP Switch Statement:

PHP switch statement is used to execute one statement from multiple conditions. It works like PHP if-else-if statement. It is a multi-way decision making statement which selects one of several alternatives based on value of an integer variable or expression. The switch statement is convenient to be used if there are large number of alternative paths. It is more efficient than if-else-if statement as several conditions need to be evaluated before a particular condition is satisfied.

Syntax:

Switch(expression)

{

Case value 1:

//code to be executed

Break;

Case value 2;

//code to be executed;

Break;

…..

Default:

Code to be executed if all cases are not matched

}

The default statement is an optional statement . Even it is not important statement. The default statement should be the last statement.There can be only one default statement , more than one default statement can lead to a fatal error.

Each case have a break statement that terminates the sequential execution of statements. Break statement is optional to use , if it is not used then all the statements will execute after finding the matched case value.

Php allows you to use string, number, character as well as functions in the switch case statement.

We can also use semi colon(;) instead of colon(:) it will not generate any error.

Example:

<?php

$num=20;

Switch($num)

{

Case 10;

Echo(“number is equal to 10”);

Break;

Case 20;

Echo(“number is equal to 20”);

Break’

Default:

Echo(”number is not equal to 10,20 and 30);

}

Output:

Number is equal to 20

PHP switch statement with characters:

We will pass a character in switch expression to check whether it is vowel or consonant. If the passed character is A, E, I, O, U, it will be vowel otherwise consonant.

<?php

$ch=’U’;

Switch(ch)

{

Case ‘a’;