php subtract variable from Array

Question

I am defining the subtraction variable like so:

    $query = "
    SELECT * FROM around WHERE `long` != '' ORDER BY id DESC"; 
    $result = mysql_query( $query );

    $select_maxlong = mysql_query("SELECT long FROM around WHERE
    `id`='$max_id'");
    $row3 = mysql_fetch_row($select_maxlong);
    $max_long = $row3[0];

Then I need to subtract $max_long from the array value below:

   while ( $row = mysql_fetch_assoc( $result ) ) {

   echo $row['long'];}

I have tried:

   foreach($row as $row) {
   $car = $max_long;
   echo "u";
   echo $car - $row['long'] ; }

But the output is not correct.

If there are 10 numbers in an array, $row['long'], I want to subtract $max_long from each of them, and echo the result.

one number of WHAT? You're fetching multiple rows of data, and subtracting a value from each of those rows. you'd have to explain what this "one number" should be, because right now your code is working perfectly well as-written. — Marc B
– Marc B, Commented Feb 12, 2015 at 20:25
How do you think if initially your $row is an array and you're doing foreach, then on first iteration $row will become a first item of $row. And what's next? — u_mulder
– u_mulder, Commented Feb 12, 2015 at 20:30
There is no more support for mysql_* functions, they are officially deprecated, no longer maintained and will be removed in the future. You should update your code with PDO or MySQLi to ensure the functionality of your project in the future. — DarkBee
– DarkBee, Commented Feb 12, 2015 at 20:42

macl · Accepted Answer · 2015-02-12 20:46:57Z

1

This code should work for you

$select_maxlong = mysql_query("SELECT long FROM around WHERE `id`='$max_id'");
$row3 = mysql_fetch_row($select_maxlong);
$max_long = $row3[0];

$myarray=array();
while ( $row = mysql_fetch_assoc( $result ) ) {
   $myarray[]=$row['long'];
}

function showvalue($element, $key) {
  echo $max_long-$element;
}

array_walk($myarray,'showvalue');

But this way, you are substracting the element from $max_long, and not otherwise as you said (that's what your code seems to try). If you want to really substract $max_long from each element of the array and output the result, just invert the variable order on the echo line. Hope this helps.

answered Feb 12, 2015 at 20:46

macl

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11 Comments

Adreamcathcer Adreamcatcher Over a year ago

Can the output be placed inside ( $row = mysql_fetch_assoc( $result ) ) { } I am trying to use JSON.

Adreamcathcer Adreamcatcher Over a year ago

The calculation worked here, but it only calculates it once. If there are 100 posts, I need it to run 100 times.

macl Over a year ago

Then you don't need to create a new array. Just do echo $max_long-$row['long']; inside the while() {...} block

macl Over a year ago

I don't think I understand... this function will echo one result per element of the original array. If there are 100, it will output 100 values.

Adreamcathcer Adreamcatcher Over a year ago

The result is 0 when I do that.

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