pg_query

(PHP 4 >= 4.2.0, PHP 5, PHP 7)

pg_query — Execute a query

Description

resource pg_query ([ resource $connection ], string $query )

pg_query() executes the query on the specified database connection. pg_query_params() should be preferred in most cases.

If an error occurs, and FALSE is returned, details of the error can be retrieved using the pg_last_error() function if the connection is valid.

Note: Although connection can be omitted, it is not recommended, since it can be the cause of hard to find bugs in scripts.

Note:
This function used to be called pg_exec(). pg_exec() is still available for compatibility reasons, but users are encouraged to use the newer name.

Parameters

connection: PostgreSQL database connection resource. When connection is not present, the default connection is used. The default connection is the last connection made by pg_connect() or pg_pconnect().
query: The SQL statement or statements to be executed. When multiple statements are passed to the function, they are automatically executed as one transaction, unless there are explicit BEGIN/COMMIT commands included in the query string. However, using multiple transactions in one function call is not recommended.

Warning
String interpolation of user-supplied data is extremely dangerous and is likely to lead to SQL injection vulnerabilities. In most cases pg_query_params() should be preferred, passing user-supplied values as parameters rather than substituting them into the query string.

Any user-supplied data substituted directly into a query string should be properly escaped.

Return Values

A query result resource on success or FALSE on failure.

Examples

Example #1 pg_query() example


<?php

$conn = pg_pconnect("dbname=publisher");
if (!$conn) {
  echo "An error occurred.\n";
  exit;
}

$result = pg_query($conn, "SELECT author, email FROM authors");
if (!$result) {
  echo "An error occurred.\n";
  exit;
}

while ($row = pg_fetch_row($result)) {
  echo "Author: $row[0]  E-mail: $row[1]";
  echo "<br />\n";
}
 
?>

Example #2 Using pg_query() with multiple statements


<?php

$conn = pg_pconnect("dbname=publisher");

// these statements will be executed as one transaction

$query = "UPDATE authors SET author=UPPER(author) WHERE id=1;";
$query .= "UPDATE authors SET author=LOWER(author) WHERE id=2;";
$query .= "UPDATE authors SET author=NULL WHERE id=3;";

pg_query($conn, $query);

?>

User Contributed Notes

hierophantNOSPAM at pcisys dot net

13 years ago


Regarding david.bouriaud@ac-rouen.fr:
You misunderstand SQL. When a query is issued, results applicable at the time of the query are returned to the application (i.e. PHP). There is no further reference to the database required. Thus, all of the pg_fetch_* functions are acting on an internal data storage, NOT the database itself. This is because SQL does not have a concept of sets, or of state (except in limited circumstances provided by transactions). However, if you use a cursor instead, fetching only one record at a time, you may get an error if you delete the table. If you don't, it is an issue with Postgres, not PHP.

a dot mcruer at live dot com

2 years ago


A quick note for novice users: when gathering input from fields on a web form that maintains a database connection, *never* use pg_query to do queries from the field. Always sanitize input using pg_prepare and pg_execute.

Akbar

11 years ago


Use pg_query to call your stored procedures, and use pg_fetch_result when getting a value (like a smallint as in this example) returned by your stored procedure.

<?php
$pgConnection = pg_connect("dbname=users user=me");

$userNameToCheckFor = "metal";

$result = pg_query($pgConnection, "SELECT howManyUsersHaveThisName('$userNameToCheckFor')");

$count = pg_fetch_result($result, 0, 'howManyUsersHaveThisName');
?>

mankyd

9 years ago


There was a typo in the code that I posted:

<?php
  $result=pg_query($conn, "SELECT * FROM x WHERE a=b;");
  if  (!$result) {
   echo "query did not execute";
  }
  if (pg_num_rows($result) == 0) {
   echo "0 records"
  }
  else {
   while ($row = pg_fetch_array($result)) {
     //do stuff with $row
   }
  }
?>

mentat at azsoft dot pl

13 years ago


$GLOBALS["PG_CONNECT"]=pg_connect(...);
....

function query ($sqlQuery,$var=0) {
   if (!$GLOBALS["PG_CONNECT"]) return 0;
   $lev=error_reporting (8); //NO WARRING!!
   $result=pg_query ($sqlQuery);
   error_reporting ($lev); //DEFAULT!!
   if (strlen ($r=pg_last_error ($GLOBALS["PG_CONNECT"]))) {
      if ($var) {
        echo "<p color=\"red\">ERROR:<pre>";
        echo $sqlQuery;
        echo "</pre>";
        echo $r;
        echo "&lt/p>";
      }
      close_db ();
      return 0;
   }
   return $result;
}

Jan-Willem Regeer

10 years ago


In reply to david dot bouriaud at ac-rouen dot fr:

All it is doing is internal caching. How can that be dangerous. If you are going to be deleting records after you have closed the connection it is your problem to make sure you have the latest and greatest records, and not some cached ones. Considering you are writing the script I don't see why it is a problem, you know what you are doing in the script, so it is quite useless for PHP to invalidate the cache, when that could be done upon exiting the script, which would mean there was less time spent cleaning out the cache when it counts most (when returning data to the user).

mankyd

9 years ago


Improving upon what jsuzuki said:

It's probably better to use pg_num_rows() to see if no rows were returned, as that leaves the resultset cursor pointed to the first row so you can use it in a loop.

Example:

<?php
  $result=pg_query($conn, "SELECT * FROM x WHERE a=b;");
  if  (!$result) {
   echo "query did not execute";
  }
  if (pg_num_rows($result) == 0) {
   echo "0 records"
  }
  else {
    while ($row = pg_fetch_array($result) {
      //do stuff with $row
    }
  }
?>

I, personally, also find it more readable.

zoli at makettinfo.hu

9 years ago


It would be better this way:

<?php
  $result=pg_query($conn, "SELECT COUNT(*) AS rows FROM x WHERE a=b;");
  if  (!$result) {
   echo "query did not execute";
  }
  if ($line = pg_fetch_assoc($result)) {
    if ($line['rows'] == 0) {
     echo "0 records"
    }
  }
  else {
   while ($row = pg_fetch_array($result)) {
     //do stuff with $row
   }
  }
?> 

This solution doesn't raise the load of the system with the move of matching rows (perhaps 0,1, perhaps 100, 1000, ... rows)

jsuzuki at spamcop dot net

10 years ago


expanding on the note left by "cmoore" -

To check to see if the recordset returned no records,

<?php
  $result=pg_query($conn, "SELECT * FROM x WHERE a=b;");
  if  (!$result) {
    echo "query did not execute";
  }
  $rs = pg_fetch_assoc($result);
  if (!$rs) {
    echo "0 records"
  }
?>

-jack

Anonymous

2 years ago


Here is my small function to make it easier for me to use data from select queries (attention, it is sensitive to sql injection)
<?php
function requestToDB($connection,$request){ 
    if(!$result=pg_query($connection,$request)){
        return False;
    }
    $combined=array();
    while ($row = pg_fetch_assoc($result)) {
        $combined[]=$row;
    }
    return $combined;
}
?>

Example:
<?php
$conn = pg_pconnect("dbname=mydatabase");

$results=requestToDB($connect,"select * from mytable");

//You can now access a "cell" of your table like this:
$rownumber=0;
$columname="mycolumn";

$mycell=$results[$rownumber][$columname];
var_dump($mycell);

cmoore

10 years ago


One thing to note that wasn't obvious to me at first.  If your query returns zero rows, that is not a "failed" query.  So the following is wrong:
  $result=pg_query($conn, "SELECT * FROM x WHERE a=b;");
  if  (!$result) {
    echo "No a=b in x\n";
  }

pg_query returns FALSE if the query can not be executed for some reason.  If the query is executed but returns zero rows then you get back a resul with no rows.

sd at dicksonlife dot com

9 years ago


Took me a while to track this down so I thought it might be useful for others:

If you use stored procedures and need to get result sets back from them:

function dbquery($link,$query){
  pg_query($link,"BEGIN;");
  $tr=pg_query($link,$query);
  $r=pg_fetch_row($tr);
  $name=$r[0];
  $rs=pg_query($link,"FETCH ALL IN \"" . $name . "\";");
  pg_query($link,"END;");
  return $rs;
}

(Error checking removed for clarity)

yoshinariatsuo at yahoo dot com

13 years ago


create table from pg_query results.. hope it helps newbies...
function table_create($result)
{
    $numrows = pg_num_rows($result);
    $fnum = pg_num_fields($result);

    echo "<table border width='100%'>";
    echo "<tr>";

    for ($x = 0; $x < $fnum; $x++) {
        echo "<td><b>";
        echo strtoupper(pg_field_name($result, $x));
        echo "</b></td>";
    }

    echo "</tr>";

    for ($i = 0; $i < $numrows; $i++) {
        $row = pg_fetch_object($result, $i);
        echo "<tr align='center'>";
        for ($x = 0; $x < $fnum; $x++) {
    $fieldname = pg_field_name($result, $x);
    echo "<td>";
    echo $row->$fieldname;
    echo "</td>";
        }
        echo"</tr>";
    }
    echo "</table>";
    
    return 0;
}

jvarner at dsrglobal dot com

13 years ago


That's why your code should never assume it has the very latest data unless it locks it.

david dot bouriaud at ac-rouen dot fr

13 years ago


Hi to all !
It seems that the old pg_exec function does not do what it is expected to.
In the doc, it is said that it returns a resource identifier on the successful querry that was send to the backend.
It seems to me that it is more than a resource identifier.
Follow the example :

<?php
$ConnId = pg_connect ("blablabla");
$ResId = pg_exec ("select * from table", $ConnId);
pg_close ($ConnId);
$row = pg_fetch_array ($ResId, 4);
?>

I closed the connection voluntarily before the pg_fetch_array. It WORKS !

Now, imagine the following script :
<?php
$ConnId = pg_connect ("blablabla");
$ResId = pg_exec ("select * from table", $ConnId);
pg_close ($ConnId);
system ("psql base -c delete from table");
$row = pg_fetch_array ($ResId, 4);
?>
See how it could be harmful !!!! I think that the coders have done this for performances reasons, but it is not the right way do do so !!!

pg_query

Description

Parameters

Return Values

Examples

See Also

User Contributed Notes