$q = "SELECT * FROM user";
$res = mysqli_query($conn, $q) or die(mysql_error());
$userList = "";
while($user = mysqli_fetch_array($res))
{
$userList .= $user['userList'].";;";
}
echo $userList;
I don't understand the while part:
Why assign the mysqli_fetch_array to $user using while?
How can the $user have index of userList?
Why concatenate with ;;?
To answer your questions:
i) mysqli_fetch_array() has two possible return values. It either returns an array of the current row that the database result set pointer points to, then advances the pointer to the next row, or it returns false if you have reached the end of the result set. The while() evaluates the value that is set to $row either continuing the loop if it is an array or stopping the loop if $row equals false
ii) The $user array has both numerical indexes for each field (i.e. 0,1,2,... [#fields - 1]) and associative indexes of the column names for the table (i.e. 'field1', 'field2', etc.). In this case one of the fields in the database is userList, so accessing $user['userList'] returns that column value for the row being worked with. BNote that the query itself would have beeter been written as SELECT userList FROM user since that is the only field you are interested in. There is no reason whatsoever to select and transfer all field data if you have no need for it. It is also rarely useful to use just mysqli_fetch_array(), as you rarely need both numerical and associative indexes on the record.It is usually best to specifically request ther associative or numerical array result depending on which you need.
iii) This code is simply building a string rather than an array of results which might be more common. For whatever reason the code writer decided values in the string should be separated by ;;.
Related
I have a script that is outputting to a CSV file. However, even though there is currently one row in the database, the output I'm getting is echoing out each column from each row in the table twice.
For example:
1,1,John,John,Smith,Smith,2014,2014
Should be
1,John,Smith,2014
This worked fine before I went with PDO and prepared statements, so I'm thinking maybe I'm not understanding how fetch() works correctly.
Below is my code. Any idea what I could be doing wrong?
// get rows
$query_get_rows = "SELECT * FROM Contacts ORDER BY date_added DESC";
$result_get_rows = $conn->prepare($query_get_rows);
$result_get_rows->execute();
$num_get_rows = $result_get_rows->rowCount();
while ($rows_get_rows = $result_get_rows->fetch())
{
$csv .= '"'.join('","', str_replace('"', '""', $rows_get_rows))."\"\n";
}
echo $csv;
exit;
You should say to PDO, that you want only an associative array or a numbered array:
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_ASSOC))
to get an associative array or
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_NUM))
to get an array indexed by the column number
from PDOStatement::fetch
fetch_style
Controls how the next row will be returned to the caller.
This value must be one of the PDO::FETCH_* constants, defaulting to
value of PDO::ATTR_DEFAULT_FETCH_MODE (which defaults to
PDO::FETCH_BOTH).
PDO::FETCH_ASSOC: returns an array indexed by column name as returned
in your result set
PDO::FETCH_BOTH (default): returns an array indexed by both column
name and 0-indexed column number as returned in your result set
I have a script that is outputting to a CSV file. However, even though there is currently one row in the database, the output I'm getting is echoing out each column from each row in the table twice.
For example:
1,1,John,John,Smith,Smith,2014,2014
Should be
1,John,Smith,2014
This worked fine before I went with PDO and prepared statements, so I'm thinking maybe I'm not understanding how fetch() works correctly.
Below is my code. Any idea what I could be doing wrong?
// get rows
$query_get_rows = "SELECT * FROM Contacts ORDER BY date_added DESC";
$result_get_rows = $conn->prepare($query_get_rows);
$result_get_rows->execute();
$num_get_rows = $result_get_rows->rowCount();
while ($rows_get_rows = $result_get_rows->fetch())
{
$csv .= '"'.join('","', str_replace('"', '""', $rows_get_rows))."\"\n";
}
echo $csv;
exit;
You should say to PDO, that you want only an associative array or a numbered array:
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_ASSOC))
to get an associative array or
while ($rows_get_rows = $result_get_rows->fetch(PDO::FETCH_NUM))
to get an array indexed by the column number
from PDOStatement::fetch
fetch_style
Controls how the next row will be returned to the caller.
This value must be one of the PDO::FETCH_* constants, defaulting to
value of PDO::ATTR_DEFAULT_FETCH_MODE (which defaults to
PDO::FETCH_BOTH).
PDO::FETCH_ASSOC: returns an array indexed by column name as returned
in your result set
PDO::FETCH_BOTH (default): returns an array indexed by both column
name and 0-indexed column number as returned in your result set
I am querying the database for all values in one column, then putting it into an associative array. The db query is working, but PHP prints an array with only one item.
<?php
$acc_names = mysqli_query($con,"SELECT acc_name FROM accounts"); #successfully returns all values in column in mysql
$acc_names = (mysqli_fetch_assoc($acc_names));
print_r($acc_names); #only one item in array
print_r($acc_names['acc_name']); #that one item
?>
You should use mysqli_fetch_all($acc_names, MYSQLI_ASSOC) instead of mysqli_fetch_assoc.
I'm getting this column in this bd
$result = mysql_query("SELECT short FROM textos");
and I'm trying to echo only one of the results based on the array it returns:
$col = mysql_fetch_assoc($result);
echo "<b>Short:</b>".$col[1]."<br/>";
apparently this $col array can't be accessed this way. How should it be done? Thanks
That has been already stated in comments above, so just a bit of explanation here.
mysql_fetch_assoc retrieves a result row for you presented as an associative array (an array where keys are field names and values are field values). Your query returns only one field (which is short), but still it doesn't make your row a single scalar value - it remains an array, only with a single element.
So you need to refer it as $row['short'], or in your sample $col['short'].
Bear in mind that query might return no results - you can learn that by checking if the returned value is not an array but scalar false instead, e.g.
if ($col === false) {
echo 'Error occured<br/>';
} else {
echo "<b>Short:</b>".$col['short']."<br/>";
}
Putting LIMIT into your query like again comments suggest is a good idea as well because you wouldn't be returning potentially huge amount of data when you only need one row actually. The result would still come as a multi-dimensional array though, so that part won't change.
To access the first element use $col[0]['short'].
If you only want to output one element anyways you can add LIMIT 1 to the MySQL query.
After querying you should check if the result array is set otherwise php will throw an error saying that $col[0]['short'] is not set.
There are three mysql_fetch functions which getting rows:
mysql_fetch_array() Fetch an array with both indexes (numeric and associative)
mysql_fetch_num() Fetch an array with numeric indexes
mysql_fetch_assoc() Fetch an array with associative indexes
In your example you will get an array that is looking like this one for the function mysql_fetch_array():
array(2) {
[0]=>
string(3) "foo"
["short"]=>
string(3) "foo"
}
$statement = 'SELECT short FROM textos';
$result = mysql_result($statement);
if ($result) {
while ($row = mysql_fetch_assoc($result)) {
var_dump($row); // or echo "<b>Short:</b>".$row['short']."<br/>"; or something else you like to do with rows of the above statement
}
}
I want to do a query in my model from a table known as jurisdictions. Now I want this query to provide a valid MySQL result resource. I.e I want to pass the result to mysql_fetch_array(). If I pass in $query = $this->db->query(). I get an error saying that the passed in argument is invalid. I was wondering how can I convert $query to a MySQL result recource.
Well, if you want to have a MySQL resource, you should be using mysql_query.
Codeigniter already has a method which will give you one row at a time: row_array (actually, it has two, the other is just row, but that returns an object, not an array). If you want to get numeric indexes on the result of result_array, use array_values:
$result = $this->db->query( "SELECT 'foo' as foo_rules FROM DUAL" );
$aso_arr = $result->row_array(); // assoc. array w/o numeric indexes
echo $aso_arr[ 'foo_rules' ];
$num_arr = array_values( $aso_arr );
echo $num_arr[ 0 ];
If you would like the entire result of the selection, then use result and result_array (they have behavior similar to row and row_array, only they return the whole result set in an array)
EDIT
I repeat my first sentence, but you can get the MySQL resource this way:
$result = $this->db->query( "SELECT 'foo' as foo_rules FROM DUAL" );
$resource = $result->result_id;
But, since this is not documented, it should not be considered supported or even expected behavior. Be forewarned.
If I'm understanding you correctly then why not just use the available methods of:
$query->result();
or
$query->result_array();
Choose whichever to suit your needs.