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

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)."'";
}
?>

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);
?>

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;
    }

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;
}
?>

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')");
?>

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)");
?>

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