Php for loop variable

Php for loop variable

• PHP Tutorial
• PHP | Introduction
• PHP Full Form
• How to set PHP development environment in windows ?
• LAMP installation and important PHP configurations on Ubuntu
• PHP | Coding Standards
• PHP | Basic Syntax
• PHP | Variables
• PHP echo and print
• PHP | Data Types
• PHP | Strings
• PHP | Constants
• PHP | Magic Constants
• PHP | Decision Making
• PHP | Loops
• PHP | Superglobals
• PHP | Regular Expressions
• PHP Examples

• Describe PHP Include and Require
• PHP | Basics of File Handling
• PHP | fopen( ) (Function open file or URL)
• PHP fread( ) Function
• PHP fclose( ) Function
• PHP | fwrite( ) Function
• PHP | Uploading File
• PHP Cookies
• PHP | Sessions
• PHP Filter and Filter Constant
• Implementing callback in PHP
• Exception Handling in PHP

• PHP | Arrays
• PHP array() Function
• PHP | array_change_key_case() Function
• PHP array_chunk() Function
• PHP | array_column() Function
• PHP array_combine() Function
• PHP array_count_values() Function
• PHP array_diff() function
• PHP array_diff_assoc() Function
• PHP array_diff_key() Function
• PHP array_diff_uassoc() Function
• PHP array_diff_ukey() Function
• PHP array_fill() function
• PHP array_fill_keys() Function
• PHP Array Functions Complete Reference

• PHP Date and Time
• PHP | checkdate() Function
• PHP | date_create(), date_format(), date_add() Functions
• PHP | date_create_from_format() Function
• PHP | date_date_set() Function
• PHP | date_default_timezone_get() Function
• PHP | date_default_timezone_set() Function
• PHP | date_diff() Function
• PHP | date_get_last_errors() Function
• PHP | date_isodate_set() Function
• PHP | date_modify() Function
• PHP | date_offset_get() Function
• PHP | date_parse_from_format() Function
• PHP | date_parse() Function
• PHP | date_sub() Function

• PHP basename( ) Function
• PHP chgrp( ) Function
• PHP chmod( ) Function
• PHP chown( ) Function
• PHP copy( ) Function
• PHP dirname( ) Function
• PHP disk_free_space( ) Function
• PHP disk_total_space( ) Function
• PHP feof( ) Function
• PHP fflush( ) Function
• PHP | fgetc( ) Function
• PHP | fgets( ) Function
• PHP | fgetss( ) Function
• PHP | file_exists( ) Function
• PHP file_get_contents() Function
• PHP Filesystem Functions Complete Reference

• PHP | ftp_alloc() function
• PHP | ftp_chdir() function
• PHP | ftp_close() function
• PHP | ftp_connect() function
• PHP | ftp_delete() function
• PHP | ftp_exec() function
• PHP | ftp_get() function
• PHP | ftp_put() function
• PHP | ftp_get_option() function
• PHP | ftp_login() function
• PHP | ftp_mdtm() Function
• PHP | ftp_mkdir() function

• PHP | Ds\Map allocate() Function
• PHP | Ds\Map apply() Function
• PHP | Ds\Map capacity() Function
• PHP | DS\Map clear() Function
• PHP | Ds\Map __construct() Function
• PHP Ds\Map copy() Function
• PHP | Ds\Map count() Function
• PHP | Ds\Map diff() Function
• PHP | Ds\Map filter() Function
• PHP | Ds\Map first() Function
• PHP Ds\Map Functions Complete Reference

• SplDoublyLinkedList in PHP
• PHP SplDoublyLinkedList add() Function
• PHP SplDoublyLinkedList bottom() Function
• PHP SplDoublyLinkedList count() function
• PHP SplFixedArray count() Function
• PHP SplFixedArray current() Function
• PHP SplFixedArray getSize() Function
• PHP SplFixedArray key() Function
• PHP SplObjectStorage addAll() Function
• PHP SplObjectStorage attach() Function
• PHP SplObjectStorage contains() Function
• PHP SplObjectStorage count() Function
• PHP SplQueue::__construct() Function
• PHP SPL Data structures Complete Reference

• PHP Tutorial
• PHP | Introduction
• PHP Full Form
• How to set PHP development environment in windows ?
• LAMP installation and important PHP configurations on Ubuntu
• PHP | Coding Standards
• PHP | Basic Syntax
• PHP | Variables
• PHP echo and print
• PHP | Data Types
• PHP | Strings
• PHP | Constants
• PHP | Magic Constants
• PHP | Decision Making
• PHP | Loops
• PHP | Superglobals
• PHP | Regular Expressions
• PHP Examples

• Describe PHP Include and Require
• PHP | Basics of File Handling
• PHP | fopen( ) (Function open file or URL)
• PHP fread( ) Function
• PHP fclose( ) Function
• PHP | fwrite( ) Function
• PHP | Uploading File
• PHP Cookies
• PHP | Sessions
• PHP Filter and Filter Constant
• Implementing callback in PHP
• Exception Handling in PHP

• PHP | Arrays
• PHP array() Function
• PHP | array_change_key_case() Function
• PHP array_chunk() Function
• PHP | array_column() Function
• PHP array_combine() Function
• PHP array_count_values() Function
• PHP array_diff() function
• PHP array_diff_assoc() Function
• PHP array_diff_key() Function
• PHP array_diff_uassoc() Function
• PHP array_diff_ukey() Function
• PHP array_fill() function
• PHP array_fill_keys() Function
• PHP Array Functions Complete Reference

• PHP Date and Time
• PHP | checkdate() Function
• PHP | date_create(), date_format(), date_add() Functions
• PHP | date_create_from_format() Function
• PHP | date_date_set() Function
• PHP | date_default_timezone_get() Function
• PHP | date_default_timezone_set() Function
• PHP | date_diff() Function
• PHP | date_get_last_errors() Function
• PHP | date_isodate_set() Function
• PHP | date_modify() Function
• PHP | date_offset_get() Function
• PHP | date_parse_from_format() Function
• PHP | date_parse() Function
• PHP | date_sub() Function

• PHP basename( ) Function
• PHP chgrp( ) Function
• PHP chmod( ) Function
• PHP chown( ) Function
• PHP copy( ) Function
• PHP dirname( ) Function
• PHP disk_free_space( ) Function
• PHP disk_total_space( ) Function
• PHP feof( ) Function
• PHP fflush( ) Function
• PHP | fgetc( ) Function
• PHP | fgets( ) Function
• PHP | fgetss( ) Function
• PHP | file_exists( ) Function
• PHP file_get_contents() Function
• PHP Filesystem Functions Complete Reference

• PHP | ftp_alloc() function
• PHP | ftp_chdir() function
• PHP | ftp_close() function
• PHP | ftp_connect() function
• PHP | ftp_delete() function
• PHP | ftp_exec() function
• PHP | ftp_get() function
• PHP | ftp_put() function
• PHP | ftp_get_option() function
• PHP | ftp_login() function
• PHP | ftp_mdtm() Function
• PHP | ftp_mkdir() function

• PHP | Ds\Map allocate() Function
• PHP | Ds\Map apply() Function
• PHP | Ds\Map capacity() Function
• PHP | DS\Map clear() Function
• PHP | Ds\Map __construct() Function
• PHP Ds\Map copy() Function
• PHP | Ds\Map count() Function
• PHP | Ds\Map diff() Function
• PHP | Ds\Map filter() Function
• PHP | Ds\Map first() Function
• PHP Ds\Map Functions Complete Reference

• SplDoublyLinkedList in PHP
• PHP SplDoublyLinkedList add() Function
• PHP SplDoublyLinkedList bottom() Function
• PHP SplDoublyLinkedList count() function
• PHP SplFixedArray count() Function
• PHP SplFixedArray current() Function
• PHP SplFixedArray getSize() Function
• PHP SplFixedArray key() Function
• PHP SplObjectStorage addAll() Function
• PHP SplObjectStorage attach() Function
• PHP SplObjectStorage contains() Function
• PHP SplObjectStorage count() Function
• PHP SplQueue::__construct() Function
• PHP SPL Data structures Complete Reference

Источник

PHP for Loop

The for loop — Loops through a block of code a specified number of times.

The PHP for Loop

The for loop is used when you know in advance how many times the script should run.

Syntax

• init counter: Initialize the loop counter value
• test counter: Evaluated for each loop iteration. If it evaluates to TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
• increment counter: Increases the loop counter value

Examples

The example below displays the numbers from 0 to 10:

Example

Example Explained

This example counts to 100 by tens:

Example

Example Explained

PHP Exercises

COLOR PICKER

Report Error

If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:

Thank You For Helping Us!

Your message has been sent to W3Schools.

Top Tutorials

Top References

Top Examples

Get Certified

W3Schools is optimized for learning and training. Examples might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Источник

Php for loop variable

for loops are the most complex loops in PHP. They behave like their C counterparts. The syntax of a for loop is:

for (expr1; expr2; expr3) statement

The first expression ( expr1 ) is evaluated (executed) once unconditionally at the beginning of the loop.

In the beginning of each iteration, expr2 is evaluated. If it evaluates to true , the loop continues and the nested statement(s) are executed. If it evaluates to false , the execution of the loop ends.

At the end of each iteration, expr3 is evaluated (executed).

Each of the expressions can be empty or contain multiple expressions separated by commas. In expr2 , all expressions separated by a comma are evaluated but the result is taken from the last part. expr2 being empty means the loop should be run indefinitely (PHP implicitly considers it as true , like C). This may not be as useless as you might think, since often you’d want to end the loop using a conditional break statement instead of using the for truth expression.

Consider the following examples. All of them display the numbers 1 through 10:

for ( $i = 1 ; ; $i ++) if ( $i > 10 ) break;
>
echo $i ;
>

Of course, the first example appears to be the nicest one (or perhaps the fourth), but you may find that being able to use empty expressions in for loops comes in handy in many occasions.

PHP also supports the alternate «colon syntax» for for loops.

for (expr1; expr2; expr3): statement . endfor;

It’s a common thing to many users to iterate through arrays like in the example below.

/*
* This is an array with some data we want to modify
* when running through the for loop.
*/
$people = array(
array( ‘name’ => ‘Kalle’ , ‘salt’ => 856412 ),
array( ‘name’ => ‘Pierre’ , ‘salt’ => 215863 )
);

for( $i = 0 ; $i < count ( $people ); ++ $i ) $people [ $i ][ 'salt' ] = mt_rand ( 000000 , 999999 );
>
?>

The above code can be slow, because the array size is fetched on every iteration. Since the size never changes, the loop be easily optimized by using an intermediate variable to store the size instead of repeatedly calling count() :

$people = array(
array( ‘name’ => ‘Kalle’ , ‘salt’ => 856412 ),
array( ‘name’ => ‘Pierre’ , ‘salt’ => 215863 )
);

for( $i = 0 , $size = count ( $people ); $i < $size ; ++ $i ) $people [ $i ][ 'salt' ] = mt_rand ( 000000 , 999999 );
>
?>

User Contributed Notes 19 notes

Looping through letters is possible. I’m amazed at how few people know that.

returns: R S T U V W X Y Z AA AB AC

Take note that you can’t use $col < 'AD'. It only works with !=
Very convenient when working with excel columns.

The point about the speed in loops is, that the middle and the last expression are executed EVERY time it loops.
So you should try to take everything that doesn’t change out of the loop.
Often you use a function to check the maximum of times it should loop. Like here:

$maxI = somewhat_calcMax ();
for ( $i = 0 ; $i somewhat_doSomethingWith ( $i );
>
?>

And here a little trick:

$maxI = somewhat_calcMax ();
for ( $i = 0 ; $i ?>

The $i gets changed after the copy for the function (post-increment).

You can use strtotime with for loops to loop through dates

Remember that for-loops don’t always need to go ‘forwards’. For example, let’s say I have the following code:

As other comments have pointed out , if «calculateLoopLength» will keep giving back the same value , it can be moved outside the loop :

$loopLength = calculateLoopLength ();
for ( $i = 0 ; $i < $loopLength ; $i ++) doSomethingWith ( $i );
>
?>

However, if the order the looping doesn’t matter (ie. each iteration is independent) then we don’t need to use an extra variable either, we can just count down (ie. loop ‘backwards’) instead:

for ( $i = calculateLoopLength (); $i > 0 ; $i —) doSomething ( $i );
>
?>

In fact, we can simplify this even more, since «$i > 0» is equivalent to «$i» (due to type casting):

for ( $i = calculateLoopLength (); $i ; $i —) doSomething ( $i );
>
?>

Finally, we can switch to a ‘pre-decrement’ instead of a ‘post-decrement’ to be slightly more efficient (see, for example, http://dfox.me/2011/04/php-most-common-mistakes-part-2-using-post-increment-instead-of-pre-increment/ ):

for ( $i = calculateLoopLength (); $i ; — $i ) doSomething ( $i );
>
?>

In this case we could also replace the entire loop with a map, which might make your algorithm clearer (although this won’t work if calculateLoopLength() == 0):

array_map ( ‘doSomething’ ,
range ( 0 , calculateLoopLength () — 1 ));
?>

Источник