SunshinePHP Developer Conference 2015

pg_fetch_assoc

(PHP 4 >= 4.3.0, PHP 5)

pg_fetch_assocHolt eine Zeile als assoziatives Array

Beschreibung

array pg_fetch_assoc ( resource $result [, int $row ] )

pg_fetch_assoc() gibt eine Zeile eines Abfrageergebnisses als assoziatives Array zurück.

pg_fetch_assoc() ist äquivalent zu pg_fetch_array() mit PGSQL_ASSOC als optionalem dritten Parameter. Zurückgegeben wird nur ein assoziatives Array. Falls Sie ein numerisches Array brauchen, müssen Sie die Funktion pg_fetch_row() benutzen.

Hinweis: Diese Funktion setzt NULL-Felder auf den PHP Wert-NULL.

pg_fetch_assoc() ist nur unwesentlich langsamer als pg_fetch_row(), aber wesentlich einfacher zu benutzen.

Parameter-Liste

result

PostgreSQL Verbindungskennung, die (unter anderem) von den Funktionen pg_query(), pg_query_params() oder pg_execute() zurückgegeben wurde.

row

Die Nummer der Zeile des Abfrageergebnisses, die geholt werden soll. Die Nummerierung beginnt bei 0. Fehlt dieser Parameter, so wird jeweils die nächste Zeile geholt.

Rückgabewerte

Ein array, das mit den Feldnamen des Abfrageergebnisses indiziert ist. Jeder Wert im array wird als string repräsentiert. Nullwerte der Datenbank (NULL) werden als NULL zurückgegeben.

Bei einem Fehler oder wenn der Parameter row größer als die Anzahl der Zeilen im Abfrageergebnis ist, oder wenn kein Datensatz mehr gelesen werden kann, wird FALSE zurückgegeben.

Changelog

Version Beschreibung
4.1.0 Der Parameter row wurde optional.

Beispiele

Beispiel #1 pg_fetch_assoc() Beispiel

<?php 
$conn 
pg_connect("dbname=publisher");
if (!
$conn) {
  echo 
"Konnte keine Verbindung aufbauen.\n";
  exit;
}

$result pg_query($conn"SELECT id, author, email FROM authors");
if (!
$result) {
  echo 
"Ein Fehler ist aufgetreten.\n";
  exit;
}

while (
$row pg_fetch_assoc($result)) {
  echo 
$row['id'];
  echo 
$row['author'];
  echo 
$row['email'];
}
?>

Siehe auch

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User Contributed Notes 15 notes

up
1
slurppp at hotmail dot fr
2 years ago
Note that all pg_fetch_* function ignoring the original type of the data and always return strings. (for numbers too)
up
1
Alexey Loktionov (error at pochta dot ru)
4 years ago
Here is much powerful pg_parse_array() variant, based on FSM: for any dimension Postgres arrays (its string representation must be well-formed), with quotation rules checks, complexity O(N), where N is a length of string representation of Postgres array:

<?php

define
('STATE_BEGIN', 1);
define('STATE_INARRAY',2);
define('STATE_OUTARRAY', 3);
define('STATE_INSLASH', 4);
define('STATE_INQUOTES', 5);

function
pg_parse_array($value) {
       
$resultArray = $indexArray = array(); $level = $index = 0;
       
$ptr = &$resultArray;
        for(
$i = 0; $i < strlen($value); $i++){
            switch(
$level){
                case
1:
                    if(
$index > 0){
                       
$ptr = & $ptr[sizeof($ptr)];
                    }
                   
$indexArray[++$index] = & $ptr;
                    break;
                case -
1:
                   
$ptr = & $indexArray[--$index];
                    break;
            }
           
$level = processFSM($value{$i}, $ptr);
        }
        return
$resultArray;
    }
   
    function
processFSM($chr, &$result){
        static
$state = STATE_BEGIN, $index = 0;
       
$level = 0;
        switch(
true){
            case
$chr == '{' && in_array($state, array(STATE_BEGIN,STATE_INARRAY,STATE_OUTARRAY), true):
               
$state = STATE_INARRAY;
               
$index = 0;
               
$level = +1;
                break;
            case
$chr == '}' && in_array($state, array(STATE_INARRAY,STATE_OUTARRAY), true):
               
$state = STATE_OUTARRAY;
               
$level = -1;
                break;
            case
$chr == '\\' && $state !== STATE_BEGIN:
               
$state = $state === STATE_INSLASH ? STATE_INQUOTES : STATE_INSLASH;
                break;
           
            case
$chr == '"' && !in_array($state, array(STATE_BEGIN,STATE_INSLASH), true):
               
$state = $state === STATE_INQUOTES ? STATE_INARRAY : STATE_INQUOTES;
                break;
           
            case
$chr == ',' && in_array($state, array(STATE_INARRAY,STATE_OUTARRAY), true):
               
$index = sizeof($result);
                break;
           
            case
$state !== STATE_BEGIN:
               
$state = $state === STATE_INSLASH ? STATE_INQUOTES : $state;
                isset(
$result[$index]) or $result[$index] = '';
               
$result[$index] .= $chr;
                break;
        }
        return
$level;
    }

?>
up
1
spam at pasher dot org
10 years ago
An important thing to note (as of PHP 4.3.2):

If you are used to using the "extended" comparision operators (=== and !==) to try to make your code easier to follow visually, this function will return NULL if the provided resource handle is invalid (as opposed to false). ie,

$rs = @pg_query('SELECT * FROM fake_table');
while (false !== ($row = @pg_fetch_assoc($rs)))
{
    print_r($row);
}

Obviously you should check to see if $rs === false before you start the while loop, but this example is used to illustrate a potential infinite loop problem if $rs IS false.
up
1
ninja (whorl) thinkninja (stop) com
11 years ago
If you are moving between different versions of PHP, this might be handy:

if (!function_exists('pg_fetch_assoc')) {
    function pg_fetch_assoc ($result)
    {
      return @pg_fetch_array($result, NULL, PGSQL_ASSOC);
    }
}
up
0
Anonymous
4 years ago
Be aware that if one of your result fields is an array, it will be output as a string using the general format of '{value1,value2, ... }' in accordance with postgres's behavior with SQL arrays.
http://www.postgresql.org/docs/8.4/static/arrays.html#ARRAYS-IO

So, here is a function to convert simple (one-dimensional) SQL arrays to PHP arrays:

<?php
function pg_parse_array($field)
/*
* Converts a simple SQL array field to its PHP equivalent.  e.g:
*
*    {null}              --> Array(null);
*    {"null"}            --> Array("null");
*    {foo,bar}           --> Array("foo", "bar");
*    {"foo,bar"}         --> Array("foo,bar");
*    {"Hello \"World\""} --> Array('Hello "World"');
*      
*/ 
{
 
// NULL fields are always NULL
 
if (!is_string($field)) return $field;

 
// Check for curly braces which may indicate an SQL array field
 
if ($field[0] != '{' or substr($field, -1) != '}') return $field;
 
$field = trim(substr($field, 1, -1));

 
$array = Array();
 
 
// Break up the string into the following:
  //  - quoted text that MAY have special chars escaped by a backslash
  //  - unquoted text that may NOT have special chars
 
$search = '/(")?+((?(1)(?:\\\\.|[^"])*|[^,]+))(?(1)\\1)/';
 
preg_match_all($search, $field, $matches, PREG_SET_ORDER);
 
  foreach(
$matches as $value)
  {
    if (
$value[1])
    {
     
// Quoted element, with backslash used to escape chars
     
$array[] = preg_replace('#\\\\(.)#', '$1', $value[2]);
    }
    else
    {
     
// Unquoted element
     
$value[2] = trim($value[2]);
      if (
strtolower($value[2]) == 'null') $array[] = null; // NULL
     
else $array[] = $value[2];
    } 
  }
  return
$array;
}

// Some tests to demonstrate this function
var_export(pg_parse_array('{null}'); // Output is Array(null);
var_export(pg_parse_array('{foo,bar}'); // Output is Array('foo', 'bar');
var_export(pg_parse_array('{"null"}'); // Output is Array('null');

?>
up
0
Anonymous
5 years ago
Beware!  If your query returns multiple columns with the same names, only the right-most one will be contained in the result array.  This can cause problems if you are using a combination of joins:

For example:
<?php
// Let's say that 'pkey' is the primary-key colum for tables a and b (primary keys are never null)
$res = pg_query("Select a.pkey, b.* FROM a LEFT JOIN b using (pkey)");
$data = pg_fetch_assoc($res);
var_dump($data['pkey']) // Is actually b.pkey, may be NULL!
?>

Both tables contain a column named 'pkey'.  Now table 'b' is on the optional side of a LEFT JOIN, so b.pkey (implicitly included via 'b.*') may be NULL.

The problem arises when you use pg_fetch_assoc(), there are two columns named 'pkey' but the result array can only contain one value per key -- in this case it will pick the one from table B instead of the one from table A, and since B is on the optional side of the left-join, $data['pkey'] may be NULL.  So if you're expecting to retrieve the column from table A, you need to use a different pg_fetch() or rewrite your query to avoid ambiguity.
up
0
Anonymous
6 years ago
bytea columns are returned escaped.
you need to call pg-unescape-bytea() on them to get the original binary back.
up
0
Anonymous
6 years ago
regarding the optional int parameter

requesting a row number that is not present in the result set is an error. don't do it.

check with pg_num_rows() beforehand, or  just use the default behavior which returns the rows in order and false after returning the last row it returns false immediately if no rows were returned.
up
0
javier dot vilarroig at gmail dot com
7 years ago
Is worth to know that when you query on multiple tables only the first row with each name is returned.

That is, if you are joining to tables with a column called 'name' you will receive only one field called name in the array and it will correspond to the one on the first table.

Is advisable to allways allias your columns in that stuation.
up
0
johniskew
7 years ago
Here is another way to iterate a resultset and display all columns in very little code... might be faster than a foreach

<?php

print '<table>';
while(
$row=pg_fetch_assoc($rs2)) print '<tr><td>'.join('</td><td>',$row2).'</td></tr>';
print
'</table>';

?>
up
0
Anonymous
8 years ago
If you request a row that does not exist, it just fails, rather than simply returning false.
up
0
Luke
9 years ago
Note:

PostgreSQL boolean values set to TRUE are returned as the string "t"

PostgreSQL boolean values set to FALSE are returned as the string "f"
up
0
petrus at bmail dot com dot au
9 years ago
$dbconn3 = pg_connect("host=127.0.0.1 port=5432 dbname=blah user=blah password=blah");
$result = pg_query($dbconn3, "SELECT * FROM Packages");

echo "<HTML><HEAD><TITLE>PostgreSQL Test Page</TITLE></HEAD><BODY>";
echo "<TABLE>";

$pkg = pg_fetch_assoc($result);
foreach ($pkg as $value) {
    echo "<TR><TD>$value";
    echo "</TR></TD>";
}

echo "</TABLE><P>";
echo "This package's full filename is: {$pkg['name']}-{$pkg['version']}{$pkg['extension']}";
echo "</BODY></HTML>";

For generating tables, this works, and personally I prefer foreach() to while loops because there's no danger of accidentally causing an infinite loop...foreach only works for as long as it has something to work with, and then stops.  I thought the echo down the bottom might come in handy, too...took me a bit to find that out.
up
0
Brenton Strickler
11 years ago
At a glance, the syntax listed at the top of this page doesn't match the example.  The PGSQL_ASSOC flag isn't necessary.
up
-1
strata_ranger at hotmail dot com
6 years ago
In a bit of follow-up to Luke's note about SQL booleans (this was a painful thing to learn the hard way), a relatively easy workaround is to typecase the boolean columns to integer inside the query, e.g:

<?php
// Assuming 'foo' is a table column of type boolean
$res = pg_query("Select foo as foo1, foo::integer as foo2 from bar");

$data = pg_fetch_assoc($res);
if (
$data['foo1']) echo 'foo1 = TRUE'; // Doesn't work as expected (string 't' and string 'f' both evaluate as TRUE)
if ($data['foo2']) echo 'foo2 = TRUE'; // Works as expected (string '0' evaluates as FALSE)
?>
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