Detailed introduction to the comparison of For, While, and Foreach loops in PHP-PHP Tutorial-php.cn

Detailed introduction to the comparison of For, While, and Foreach loops in PHP

黄舟

Release： 2023-03-06 20:52:01

Original

1894 people have browsed it

In the process of using PHP as a programming language, we often encounter situations where we need to execute a piece of code multiple times. At this time, you need to use PHP loop. PHP provides three different types of loops for you to use in appropriate scenarios:

<a href="http://www.php.cn/wiki/125.html" target="_blank">For</a> Loop
<a href="http://www.php.cn/wiki/121.html" target="_blank">While</a> Loop
##Foreach<a href="http://www.php.cn/wiki/127.html" target="_blank"></a> Loop

For Loop

The for loop is used when you have determined how many times your

expression needs to be executed.

Syntax:

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

Copy after login

<p style="margin-top: 6px;"><?phpfor($i=1; $i<=100000; $i++)<br/>{    echo "The number is " . $i . "<br>";<br>}?><br></p>

Copy after login

While loop

The while expression will execute a section of code until the conditional statement is false. While loops are generally better suited for database related operations.

Syntax:

while (condition)
{
    code to be executed;
}

Copy after login

<!--?php// If you had an array with fruit names and prices in you could use foreach$fruit = array( 
    "orange" =--> "5.00", 
    "apple" => "2.50", 
    "banana" => "3.99" ); 

foreach ($fruit as $key => $value) { 
    "$key is $value dollars 
";
} 

?>

Copy after login

Comparison of three types of loops

We know that there are many kinds of loops in PHP,

Now we need to know which loop is more Efficient so that the applications we write can be faster.

Let’s start the experiment for comparison.

While loop vs. For loop

<?php    // While Loop    $a=0;    while($a < 1000)
    {
        $a++;
    }?>

Copy after login

VS.

<?php    // For Loop    for($a = 0; $a < 1000;)
    {
        $a++;
    }?>

Copy after login

The above experiment proves that while loop is better than For loop execution efficiency is 19.71% higher. Therefore, it is recommended to use while loops instead of For loops whenever possible.

For Loop vs Foreach Loop

<?php   
 $test = array(1 => "cat", "dog" => 0, "red" => "green", 5 => 4, 3, "me");    
$keys = array_keys($test);    $size = sizeOf($keys);    for($a = 0; $a < $size; $a++)
    {        $t = $test[$keys[$a]];
    }?>

Copy after login

VS.

<?php    $
test = array(1 => "cat", "dog" => 0, "red" => "green", 5 => 4, 3, "me");   
 foreach($test as $t){
    
    }?>

Copy after login

The above experiment proves that

Foreach loop is 141.29% faster than For loop !

Conclusion

These loops are usually used to achieve different purposes, and now we know how each loop performs in terms of execution efficiency. When execution efficiency needs to be pursued, we usually recommend using while loops instead of for loops. Similarly, between the foreach loop and the loop loop, use the foreach loop as much as possible. Next, we'll look at how to effectively use loops in templates. Please stay tuned.

The above is the detailed content of Detailed introduction to the comparison of For, While, and Foreach loops in PHP. For more information, please follow other related articles on the PHP Chinese website!