PHP - Multiple conditions in while statement

Question

For some reason this code won't run in my compiler. The intention (as part of a larger project) is to ping a particular host 3 times, or until successful, whichever comes first. It's not producing any errors, just terminating. It works just fine if I remove the second condition from the while statement, but then I would need to have something more complicated to terminate the loop on a successful ping. I haven't touched PHP in a while, so I'm probably missing something stupid.

<?php
function pingAddress($ip) {
//Set variable to limit loops and end if live
$pass = 0;
$result = 0;
//Create conditions for while loop
while( ( $pass < 3 ) && ( $result = 0 ) ) {
    //Count loops
    $pass++;
    //Execute ping
    $output=shell_exec('ping -n 1 '.$ip);
    //Display ping results for testing purposes
    echo "<pre>$output</pre>";
    //Check for "TTL" presence
    if(strpos($output, 'TTL') !== false)
    {
        //Notate positive result
        $result++;
        //Display for testing
        echo "Alive";
    }
    //Display negative result for testing
    else
    {
        echo "Dead";
    }
}
}


PingAddress("8.8.8.8");

Need a double == in `$result = 0`, this is just assigning 0 to $result not testing it. — Nigel Ren, Jul 13 '18 at 15:31
Possible duplicate of [The 3 different equals](https://stackoverflow.com/questions/2063480/the-3-different-equals) — Patrick Q, Jul 13 '18 at 15:34
You could use https://en.wikipedia.org/wiki/Yoda_conditions to avoid this error. — A.L, Jul 13 '18 at 15:37

score 6 · Accepted Answer · answered Jul 13 '18 at 15:32

6

You'll kick yourself:

while( ( $pass < 3 ) && ( $result = 0 ) ) {

Should use a double equals - it's a comparison, not an assignment:

while( ( $pass < 3 ) && ( $result == 0 ) ) {

answered Jul 13 '18 at 15:32

RichardAtHome

4,293
4
20
29

Felippe Duarte · Answer 2 · 2018-07-13T15:43:16.813

You don't need the second variable $result. Use break instead.

while($pass < 3) {
    //Count loops
    $pass++;
    //Execute ping
    $output=shell_exec('ping -n 1 '.$ip);
    //Display ping results for testing purposes
    echo "<pre>$output</pre>";
    //Check for "TTL" presence
    if(strpos($output, 'TTL') !== false)
    {
        //Display for testing
        echo "Alive";

        break; //exiting while loop
    }
    //Display negative result for testing
    else
    {
        echo "Dead";
    }
}

You can even write less code with

while($pass++ < 3) {

score 0 · Answer 3 · answered Jul 13 '18 at 15:32

0

Your second condition is written incorrectly. Change it to $result === 0

answered Jul 13 '18 at 15:32

Jon Wyatt

79
6

score 0 · Answer 4 · answered Jul 13 '18 at 15:33

0

Use equal operator not assign.

while( ( $pass < 3 ) && ( $result == 0 ) )

This should work.

answered Jul 13 '18 at 15:33

Mateusz Byczkowski

326
2
11

PHP - Multiple conditions in while statement

4 Answers4