How can I populate a javascript array with values from a database using PHP?

Collect the values in an array and convert it to JSON with json_encode:

$array = array();
while ($row = mysql_fetch_assoc($result)) {
    $array[] = $row['key'];
}
echo 'var array = '.json_encode($array).';';

Answer 1: yes, it can be done.

Answer 2: Here's how:

$js_array = "[";
$result = mysql_query("some query of yours");
while( $row=mysql_fetch_array($result, MYSQL_NUM) ) {
    $js_array .= $row[0]; // assuming you just want the first field 
                          // of each row in the array
    $js_array .= ",";
}
$js_array{ strlen($js_array)-1 } = ']';

echo "var db_array = $js_array ;";

Cheers!

<script language="javascript1.2">
var arr = new array(<?php 
$result = mysql_query("select .... ");
$count = mysql_num_rows($result);
if($count>0){
  for( $i=0;$i<$count-1;$i++) {
    $row = mysql_fetch_row($result);
    echo $row[0],',';
  }
  $row = mysql_fetch_row($result);
  echo $row[0],',';
}
?>);
</script>

If you can loop through the database contents, creating an array is simple:

echo "var myArray = [";

Loop through array here and add commas to separate values.

echo "];";

Your myArray variable will be available client-side. It should look something like:

var myArray = [1, 3, 2, 4];

Alternatively and to avoid an extra comma due to loop-based string concatenation, you can write the variable to the client as follows:

echo "var myArray = [];"

...and do the following for each data row:

echo "myArray.push($db_data);"

This is effective, though not quite as clean as the previous approach. You will end up with code similar to the following:

var myArray = [];

myArray.push(3);
myArray.push(5);
myArray.push(1);

alert(myArray); // will display "3, 5, 1"

My apologies for not being too familiar with PHP, but this is something that can be done with any server-side language.

Here is a solution that correctly deals with single quotes in the data:

First retrieve the database data, for example with mysqli_ functions:

$result = mysqli_query($con, $sql);
if (!$result) die(); // error handling comes here
$array = mysqli_fetch_all($result, MYSQLI_ASSOC);

Then convert it to JSON, escape single quotes and output the JavaScript:

$output = str_replace("'", "\'", json_encode($array));
echo "var array = '$output';";

Note that json_encode escapes backslashes (as it should) by doubling them. And it is normal that it does not escape single quotes, as it cannot know the context we put it in. So when we inject it in JavaScript, wrapping it in single quotes, we are also responsible for escaping the quotes.