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
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() 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 ('$immagine_con_escape'::bytea);PostgreSQL 7.2.2 e successivi non necessitano del cast. L'eccezione è che quando le codifiche di carattere del client e del backend non corrispondono, ci possono essere errori del flusso multi-byte. L'utente deve effettuare un cast a bytea per evitare questo errore.Le nuove versioni di PostgreSQL avranno il supporto per la funzione di unescape. Il supporto per la funzione unescape verrà aggiunto non appena disponibile.
See also pg_escape_string()
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User Contributed Notes 7 notes
ynzhang from lakeheadu of ca ¶
15 years ago
Hayley Watson ¶
7 years ago
PostgreSQL 9.0 introduced a new hexadecimal-based representation for bytea data that is preferred over the escaping mechanism implemented by this function.
<?php
function pg_escape_byteahex($binary)
{
return "E'\\\\x".bin2hex($binary)."'";
}
?>
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($raw);
?>
Mocha ¶
21 years ago
to unescape_bytea use stripcslashes(). If you need to escape bytea and don't have pg_escape_bytea() function then use:
<?php
function escByteA($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;
}
?>
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')");
?>
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'$escaped'::bytea)");
?>
php at tobias dot olsson dot be ¶
22 years ago
if you need to change back bytea from the db to normal data, this will do that:
<?php
function pg_unescape_bytea($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
