Pdo:exec () A question about the return value

Pdo::exec () The return value of the problem.
Set script run time to unlimited
Set_time_limit (0);

Create a pgsql connection with PDO
try {
$pgLink = new PDO (' Pgsql:host=localhost port=5432 dbname=db2 user=root password=111111 ');
}catch (Exception $e) {
echo $e->getmessage ();
}

Defining SQL Modification Statements
$sql = "UPDATE trade.membership SET gender=1, birth_type=0, name= ' wsy ', birthday= ' 2011-01-01 ', email= ', join_date= ' 2011 -01-02 ', Status=1, address= ' aaaa ', id_number= ' 25454 ', postcode= ' 100031 ', phone= ' 666 ', type_id=1 WHERE mobile= ' 110 '; ";

Execute SQL statement
$result = $pgLink->exec ($sql);

Output SQL Results
echo $result. ' '. $sql;

Output Result:
1 UPDATE trade.membership SET gender=1, birth_type=0, name= ' wsy ', birthday= ' 2011-01-01 ', email= ', join_date= ' 2011-01-02 ', Status=1, address= ' aaaa ', id_number= ' 25454 ', postcode= ' 100031 ', phone= ' 666 ', type_id=1 WHERE mobile= ' 110 ' ;

The problem is this:
This table has no mobile= ' 110 ' this line, the $SQL statement to the local SQL Server run is also "0 affected rows."
But why is the result in the program "1"? The output of pdo::exec () should not be the number of rows affected by adding or deleting.

------Solution--------------------
This should be a bug of PDO, which can be processed correctly using preprocessing and Pdo::rowcount ().

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