Tuesday, September 22, 2020

Loops in PHP



Hello dear readers! welcome back to another section of my tutorial on PHP. In this tutorial guide, we will be discussing about the PHP Loops.

Loops are used to execute the same block of code a specified number of times. PHP supports the following four types of loops -

  • for loop - loops through a block of code in a specified number of times.
  • while loop - loops through a block of code if and as long as the specified condition is true.
  • do...while loop - This loops through a block of code only once, and then repeats the loop as long as a specified condition is true.
  • foreach loop - loops through a block of code for each of the element in an array.

In this tutorial post, we will also be discussing about the break and continue statements used for controlling loop execution.

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The for loop statement

The PHP for loop statement is used when you know how many times that you want to execute a statement.

Flowchart


Syntax

for (initialization; condition; increment){
   code to be executed;
}

The initializer is used to set the start value for the counter of the number of loop iterations. You can declare a variable here for this purpose and and it is very much traditional to name it $i.

Example

The following example makes five iterations and then changes the assigned value of two variables on each pass of the loop -

  <html>
   <body>
      
      <?php
         $a = 0;
         $b = 0;
         
         for( $i = 0; $i<5; $i++ ) {
            $a += 10;
            $b += 5;
         }
         
         echo ("At the end of the loop a = $a and b = $b" );
      ?>
   
   </body>
</html>

Output

When the above code is executed, it will produce the following result -

  At the end of the loop a = 50 and b = 25

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The while loop statement

The while loop statement will execute a block of code if and as long as a test expression is true.

If a test expression is true, then the code block will be executed. After the code has executed, the test expression will yet again be evaluated and the loop is going to continue until test expression is found to be false.

Flowchart

Syntax

  while (condition) {
   code to be executed;
}

Example

The example below decrements a variable value on each iteration and the counter increments untill it reaches 10 when the evaluation is false and the loop ends.

  <html>
   <body>
   
      <?php
         $i = 0;
         $num = 50;
         
         while( $i < 10) {
            $num--;
            $i++;
         }
         
         echo ("Loop stopped at i = $i and num = $num" );
      ?>
      
   </body>
</html>

Output

When the above code is executed, it will produce the following result -

  Loop stopped at i = 10 and num = 40 

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The do...while loop statement

The do....while loop statement will execute a block of at least once. It will then repeat the loop as long as a condition is true.

Syntax

  do {
   code to be executed;
}
while (condition);

Example

The example will increments the value of i at least once, and it is going to continue incrementing the variable i as long as it has a value less than 10 -

  <html>
   <body>
   
      <?php
         $i = 0;
         $num = 0;
         
         do {
            $i++;
         }
         
         while( $i < 10 );
         echo ("Loop stopped at i = $i" );
      ?>
      
   </body>
</html>

Output

When the above code is executed, it will produce the following result -

  Loop stopped at i = 10

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The foreach loop statement

The foreach statement is used to loop through arrays. For each of the pass, the value of the current array element is allotted to $value and the array pointer is moved by one and in the next pass, the next element is going to be processed.

Syntax

foreach (array as value) {
   code to be executed;
}

Example

Try the following example to list out the values of an array.

<html>
   <body>
   
      <?php
         $array = array( 1, 2, 3, 4, 5);
         
         foreach( $array as $value ) {
            echo "Value is $value <br />";
         }
      ?>
      
   </body>
</html>

Output

When the above code is executed, it will produce the following result -

Value is 1
Value is 2
Value is 3
Value is 4
Value is 5



The break statement

The break statement is used to terminate the execution of a loop prematurely.

The break statement is situated inside of the statement block. It gives you full control of the loop and whenever you want to exit from the loop, you can come out of it. After coming out from the loop, the immediate statement to the loop will be executed.

Flowchart


Example

In the following below example, the condition test becomes true when the counter value reaches 3 and the loop terminates.

  <html>
   <body>
   
      <?php
         $i = 0;
         
         while( $i < 10) {
            $i++;
            if( $i == 3 )break;
         }
         echo ("Loop stopped at i = $i" );
      ?>
   
   </body>
</html>

Output

When the above code is executed, it will produce the following result -

  Loop stopped at i = 3



The continue statement
The continue statement is used to halt the current iteration of a loop but it doesn't terminate the loop.

Just like the break statement, the continue statement is situated inside of the statement block containing the code that the loop executes, which is followed by a conditional test. For the pass facing continue statement, rest of the loop code is skipped and next pass starts.

Flowchart

Example
In the example below, loop prints the value of an array but for which condition becomes true it skips the code and next value is printed.

  <html>
   <body>
   
      <?php
         $array = array( 1, 2, 3, 4, 5);
         
         foreach( $array as $value ) {
            if( $value == 3 )continue;
            echo "Value is $value <br />";
         }
      ?>
   
   </body>
</html>

Output
When the above is executed, it will produce the following result -

Value is 1
Value is 2
Value is 4
Value is 5


Alright guys! This is where we are rounding up for this tutorial post. In my next tutorial post, we are going to be discussing about the PHP Arrays.

Feel free to ask your questions where necessary and i will attend to them as soon as possible. If this tutorial was helpful to you, you can use the share button to share this tutorial.

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Thanks for reading and bye for now.
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