pg_escape_bytea

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

pg_escape_bytea — Aggiunge le sequenze di escape ai dati binari nel tipo bytea

Descrizione

pg_escape_bytea(string $dati): string

pg_escape_bytea() aggiunge le sequenze di escape nei dati di tipo bytea. Restituisce una stringa con le sequenze.

Nota:
Quando si esegue una SELECT su un tipo bytea, PostgreSQL restituisce dei byte formattati in ottale e con il prefisso \ (es. \032). Agli utenti è lasciato il compito di convertire questi valori in formato binario.

Questa funzione richiede una versione di PostgreSQL pari o superiore alla 7.2. Con PostgreSQL 7.2.0 e 7.2.1, il tipo bytea richiede un cast quando si abilita il supporto multi-byte. Es. INSERT INTO tabella (immagine) VALUES ('$immagine_con_escape'::bytea); PostgreSQL 7.2.2 e successivi non necessitano del cast. L'eccezione è che quando le codifiche di carattere del client e del backend non corrispondono, ci possono essere errori del flusso multi-byte. L'utente deve effettuare un cast a bytea per evitare questo errore.

Le nuove versioni di PostgreSQL avranno il supporto per la funzione di unescape. Il supporto per la funzione unescape verrà aggiunto non appena disponibile.

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User Contributed Notes 8 notes

down

ynzhang from lakeheadu of ca ¶

15 years ago

The reason pg_unescape_bytea() do not exactly reproduce the binary data created by pg_escape_bytea() is because the backslash \ and single quote ' are double escaped by the pg_escape_bytea() function. This will lead to image seems corrupted when retrieve from the bytea field. The proper way to escape&unescape a binary string into a PG bytea field as follow:



<?php

$escaped_data = str_replace(array("\\\\", "''"), array("\\", "'"), pg_escape_bytea($data));

/* and later unescape the escaped data from the bytea field with following to get the original binary data */



$original_data = pg_unescape_bytea($escaped_data));

?>



more details at: http://archives.postgresql.org/pgsql-php/2007-02/msg00014.php

down

Hayley Watson ¶

7 years ago

PostgreSQL 9.0 introduced a new hexadecimal-based representation for bytea data that is preferred over the escaping mechanism implemented by this function.

<?php
function pg_escape_byteahex($binary)
{
    return "E'\\\\x".bin2hex($binary)."'";
}
?>

down

Mike-RaWare ¶

14 years ago

To prevent any problems with encoding you could use hexadecimal or base64 input to save and retrieve data to the database:

<?php 
  // Connect to the database
  $dbconn = pg_connect( 'dbname=foo' );
  
  // Read in a binary file
  $data = file_get_contents( 'image1.jpg' );
  
  // Escape the binary data
  $escaped = bin2hex( $data );
  
  // Insert it into the database
  pg_query( "INSERT INTO gallery (name, data) VALUES ('Pine trees', decode('{$escaped}' , 'hex'))" );

  // Get the bytea data
  $res = pg_query("SELECT encode(data, 'base64') AS data FROM gallery WHERE name='Pine trees'");  
  $raw = pg_fetch_result($res, 'data');
  
  // Convert to binary and send to the browser
  header('Content-type: image/jpeg');
  echo base64_decode($raw);
?>

down

Mocha ¶

21 years ago

to unescape_bytea use stripcslashes(). If you need to escape bytea and don't have pg_escape_bytea() function then use:



<?php

function escByteA($binData) {

  /**

   * \134 = 92 = backslash, \000 = 00 = NULL, \047 = 39 = Single Quote

   *

   * str_replace() replaces the searches array in order. Therefore, we must

   * process the 'backslash' character first. If we process it last, it'll

   * replace all the escaped backslashes from the other searches that came

   * before.

   */

  $search = array(chr(92), chr(0), chr(39));

  $replace = array('\\\134', '\\\000', '\\\047');

  $binData = str_replace($search, $replace, $binData);

  return $binData;

  //echo "<pre>$binData</pre>";

  //exit;

}

?>

down

tabflo at gmx dot at ¶

3 months ago

this method des the same as pg_escape_bytea have fun with it:

public function escape_bytea($data) {
        $escaped = '';

        for ($i = 0; $i < strlen($data); $i++) {
            $char = $data[$i];
            $ascii = ord($char);

            $escaped.= ($ascii < 32 || $ascii > 126 ? sprintf('\\%03o', $ascii) : ($char == '\\' ? '\\\\' : $char) );
        }
        return $escaped;
    }

down

Michael ¶

10 years ago

using  pg_escape_bytea without 'E' escape tag
<?php 
  // Die Binärdaten maskieren
  $escaped = pg_escape_bytea($data);

  // und in die Datenbank einfügen (falsch/wrong)
  pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', E'$escaped')");

  // und in die Datenbank einfügen (richtig/right)
  pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', '$escaped')");
?>

down

gglockner AT NOSPAMdwaffler DOT com ¶

15 years ago

If you're getting errors about nonstandard use of \\ in a string literal, then you need to escape the encoded bytea as follows:



<?php

$escaped = pg_escape_bytea($data);

pg_query("INSERT INTO gallery (name, data) VALUES ('Pine trees', E'$escaped'::bytea)");

?>

down

-3

php at tobias dot olsson dot be ¶

22 years ago

if you need to change back bytea from the db to normal data, this will do that:



<?php

function pg_unescape_bytea($bytea) {

return eval("return \"".str_replace('$', '\\$', str_replace('"', '\\"', $bytea))."\";");

}



// use like this

$rs = pg_query($conn, "SELECT image from images LIMIT 1");

$image = pg_unescape_bytea(pg_fetch_result($rs, 0, 0));

?>



/Tobias

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