How to retrieve the data from array in PHP

Question

I have populated an array using explode from a comma separated string variable. Now I need to access the data in the array.

I used:

print_r($values); // to see how the data was stored
//output
Array ( 
  [0] => Array ( 
         [0] => 1rv09is001 
         [1] => 07IS72 ) 
  [1] => Array ( 
         [0] => 1RV09IS064   
         [1] => 07IS72 ) 
)

I tried:

$a = count($values);
for($i;$i<$a;$i++){
$sql="UPDATE subject 
      SET attendance=attendance+1 
      WHERE usn=$values[$i][0] AND subCode=$values[$i][1]
     ";

echo "$sql";
mysql_query($sql);
}

It isn't working.

The mysql_* functions are deprecated, use PDO or mysqli_* instead. — nkr
– nkr, Commented Nov 3, 2012 at 12:06

Madara's Ghost · Accepted Answer · 2012-11-03 12:11:58Z

1

Complex variable names (or arrays, for that matter) need to be enclosed in curly brackets when used inside of strings. Also, strings in MySQL need to be designated as such with quotes (single ' or double "):

$a = count($values);
for ($i = 0; $i < $a; $i++) {
    $sql = "UPDATE subject SET attendance=attendance+1 WHERE usn='{$values[$i][0]}'  AND subCode='{$values[$i][1]}'";
    echo "$sql";
    mysql_query($sql);
}

Also, you need to initialize $i with a value when used in a for loop.

answered Nov 3, 2012 at 12:11

Madara's Ghost

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1 Comment

Muthu Kumaran Over a year ago

$values[$i][0] is a string, you need to put single quotes

nikita2206 · Accepted Answer · 2012-11-03 12:13:12Z

0

You should quote strings that goes into your sql (also you should escape them). http://dev.mysql.com/doc/refman/5.0/en/entering-queries.html

answered Nov 3, 2012 at 12:13

nikita2206

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2 Comments

Elias Van Ootegem Over a year ago

He shouldn't escape them, he should use prepared statements

nikita2206 Over a year ago

Of course, but now he won't get the concept of binding variables/values. I think at first he should understand the basics.

Peter Ilfrich · Accepted Answer · 2012-11-03 12:15:26Z

0

Update your SQL statement:

$sql = "UPDATE subject SET attendance = attendance+1 where usn='" . $values[$i][0] . "' and subCode='" . $values[$i][1] . "'";

As far as I can see $values contains String values, which need to be quoted in SQL. Furthermore it is helpful to escape " . $variable . " array accesses.

Tested it locally and it works.

edited Nov 3, 2012 at 12:15

answered Nov 3, 2012 at 12:08

Peter Ilfrich

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2 Comments

Bala Over a year ago

i printed the $sql and it turned out UPDATE subject SET attendance=attendance+1 WHERE usn='Array[0]' AND subCode='Array[1]'

Peter Ilfrich Over a year ago

Try to put echo mysql_error(); after your statement or submit the $sql manually to the database via PHPmyAdmin to get some error message.

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