fetchColumn return boolean false when a row not is found or don't had more rows.
(PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo >= 0.9.0)
PDOStatement::fetchColumn — Returns a single column from the next row of a result set
Returns a single column from the next row of a result set or false if
there are no more rows.
Nota:
PDOStatement::fetchColumn() should not be used to retrieve boolean columns, as it is impossible to distinguish a value of
falsefrom there being no more rows to retrieve. Use PDOStatement::fetch() instead.
column0-indexed number of the column you wish to retrieve from the row. If no value is supplied, PDOStatement::fetchColumn() fetches the first column.
PDOStatement::fetchColumn() returns a single column
from the next row of a result set or false if there are no more rows.
There is no way to return another column from the same row if you use PDOStatement::fetchColumn() to retrieve data.
Emits an error with level E_WARNING if the attribute PDO::ATTR_ERRMODE is set
to PDO::ERRMODE_WARNING.
Throws a PDOException if the attribute PDO::ATTR_ERRMODE
is set to PDO::ERRMODE_EXCEPTION.
Example #1 Return first column of the next row
<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();
print "Fetch the first column from the first row in the result set:\n";
$result = $sth->fetchColumn();
print "name = $result\n";
print "Fetch the second column from the second row in the result set:\n";
$result = $sth->fetchColumn(1);
print "colour = $result\n";
?>Il precedente esempio visualizzerà:
Fetch the first column from the first row in the result set: name = lemon Fetch the second column from the second row in the result set: colour = red
fetchColumn return boolean false when a row not is found or don't had more rows.This is an excellent method for returning a column count. For example:
<?php
$db = new PDO('mysql:host=localhost;dbname=pictures','user','password');
$pics = $db->query('SELECT COUNT(id) FROM pics');
$this->totalpics = $pics->fetchColumn();
$db = null;
?>
In my case $pics->fetchColumn() returns 641 because that is how many pictures I have in my db.When migrating from mysqli it is important that while mysqli_result::fetch_column will iterate over subsequent rows PDOStatement::fetchColumn will NOT!
<?php
while ( $row0 = $db->query("SELECT `value` FROM `bool`")->fetchColumn(0) ) {
var_dump( $row0 );
}
?>
is an endless loop unless the first column in the first row of the table bool is "0".