How to Implement while and do...while Loops in PHP

When writing code you often need to execute the same block repeatedly; loops allow this without duplicating code.

PHP while loop

The while loop runs its block as long as a given condition evaluates to true.

In PHP the available loop statements are:

while – executes the block while the condition is true

do...while – executes the block once, then repeats while the condition is true

for – repeats a block a specified number of times

foreach – iterates over each element of an array

PHP while loop syntax

<code>while (condition) {</code><code>    // code to execute</code><code>}</code>

Example: initialize $x = 1 , then increment it while it is less than or equal to 5.

<code>&lt;?php</code><code>$x = 1;</code><code>while ($x <= 5) {</code><code>    echo "这个数字是：$x <br>";</code><code>    $x++;</code><code>}</code><code>?&gt;</code>

PHP do...while loop

The do...while loop executes its block once before checking the condition; if the condition is true, it repeats.

Syntax:

<code>do {</code><code>    // code to execute</code><code>} while (condition);</code>

Example: start with $x = 1 , output the value, increment, and continue while $x <= 5 .

<code>&lt;?php</code><code>$x = 1;</code><code>do {</code><code>    echo "这个数字是：$x <br>";</code><code>    $x++;</code><code>} while ($x <= 5);</code><code>?&gt;</code>

Note that a do...while loop always runs its body at least once, even if the condition is false on the first check.

Another example sets $x = 6 ; the loop runs once, then the condition ( $x <= 5 ) fails, so it stops.

<code>&lt;?php</code><code>$x = 6;</code><code>do {</code><code>    echo "这个数字是：$x <br>";</code><code>    $x++;</code><code>} while ($x <= 5);</code><code>?&gt;</code>